A GARMENT FIELD OF THE INVENTION The invention relates to a garment. BACKGROUND OF THE INVENTION Known garments comprise various alternatives, such as playsuits, trou- sers, or T-shirts. One problem associated with the known garments is that they comprise complicated fasteners, such as buttons. A problem related to certain known garments is that they must be pulled over the head when dressing or taking off the garment. Further, a problem related to the known garments is that they must be changed even if a small area of the garment gets dirty. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a whole new solution. The objects of the invention are achieved by a garment which is characterized by what is stated in the independent claim. The preferred embodiments of the inven- tion are disclosed in the dependent claims. The garment comprising two detached parts comprises several ad- vantages: The garment is easy and quick to dress. It can be dressed without pulling over a head and without checking the front and back side. There is an easy access to a crotch. The garment is warm but allows motion. Due to the structure of the garment there is less laundry and a great number of different outfits. The garment comprises a reduced number of seams. The garment comprises a minimum num- ber of fasteners, such as buttons, zippers, or hook and loop tapes. The garment is preferably for a human being, i.e. a user of the garment may be of any age, e.g. a baby or an aged person. The garment may also be applied to non-human applications, such as e.g. pet clothing, especially dog clothing, or doll clothing that resembles baby clothing. The garment comprises two detached garment parts that are mirror im- ages to each other when dressed. The detached garment parts are cut by using identical patterns. The garment parts do not have any seam that joins them to- gether. The garment part comprises a torso portion. The torso portion is di- vided in two sides in the cross-direction of the torso portion by a central longitudi- nal axis. The garment part comprises only one leg and only one shoulder section. The leg and the shoulder section may be on opposite sides of the central longitudinal axis of the garment part, or they may be on the same side of the central longitudinal axis. The shoulder section means that there is at least a strap or a like which is intended to extend over a shoulder. Usually there is a shoulder section having an arm hole. A sleeve may be attached to the arm hole, or the garment part may be sleeveless. As the garment comprises two detached garment parts the garment is easy to put on. No pulling over a user´s head is required because the user can be dressed from under. This is important especially in connection with a lying person, such as a baby, or a bedridden patient, or a hospitalized patient. The garment is also advantageous for people that have limited mobility, i.e. the garment is easy to dress although limbs are stiff. The garment provides an easy access to a user´s crotch since the de- tached garment parts can be distanced from each other because there is not any seam or fastener that joins the garment parts in the crotch. It makes e.g. a diaper changing and checking easy and quick. The garment is warm because there are two layers of fabric on the torso portion. At the same time the garment allows free motion since parts that cover limbs have only one layer of fabric. The garment provides a great number of outfits since the garment parts can be used in various combinations. One may pick two garment parts from a se- lection of the garment parts. When one of the two garment parts gets dirty one can pick another garment part from the selection and the use of the other part can con- tinue, or one may dress the garment parts in a different order so that the dirty part is under the clean part on the torso portion. As a consequence, there is less laundry. The garment comprises a reduced number of seams and a minimum number of fasteners. For example, no fasteners are required in order to open or close the torso portion. Thus, the garment is comfortable and pressure indenta- tions to the skin of the user are reduced. As the garment can be changed partly, i.e. only one garment part is changed, and there are the minimum number of the fasteners the garment is sus- tainable. Less laundry means enhanced environmental sustainability and the gar- ment without many fasteners is easy to recycle. The garment is suitable for many uses. It may be used e.g. as a babywear, sleepwear, daywear, or sportswear. Its material may be of any textile fiber or blends of fibers in a form of a fabric, such as a weave or a knit. There may also be different materials in the same garment part. The grainline of the fabric may vary. The seams of the garment may be made by various techniques, such as sewing, glu- ing, or knitting. The garment may have a single color or it may be multi-colored. The garment may be of any size. Its dimensions may be changed when required, e.g. slim or baggy designs are possible. The garment may comprise various details, such as pockets, fasteners, decorative seams, or other decorations, e.g. embroideries or frills. The garment may also comprise seams that are placed differently or additional seams. Edges of the garment, such as edges of neck or leg openings, may comprise elastic material, such as rubber bands or elastic stitching. Further, the edges may comprise material that differs from the rest of the garment, such as an edge tape. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figures 1 to 4 and 6 show front views of a garment part; Figure 5 shows pieces of a garment part; Figures 7 and 8 show front views of garment parts and garments. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a front view of a garment part 1, i.e. it shows the front side of the garment part 1. The back side of the garment part 1 is a mirror image of the front side. The garment part 1 comprises a torso portion 2, which is divided in two sides by a central longitudinal axis CLA. The central longitudinal axis CLA runs through a neckline 4 and a crotch 5. A leg 6 and a sleeve 7 are attached to the torso portion 2. There may be a seam 8 between the torso portion 2 and the sleeve 7. The sleeve 7 is attached to a shoulder section 3, which extends from the front side of the garment part 1 to the back side of the garment part 1. The shoulder section 3 comprises in Fig.1 a front piece and a back piece that are joined at the shoulder section 3. In Fig.1 there is a sleeve 7 but it is also possible that there is only an arm hole 9, i.e. the garment part 1 is sleeveless as shown in Fig.2.^It is also possible that the shoulder section 3 comprises at least one strap, which extends from the front side to the back side. The leg 6 and the shoulder section 3 are on the opposite sides of the central longitudinal axis CLA. Figure 3 shows a front view of a garment part 1, i.e. it shows the front side of the garment part 1. The back side of the garment part 1 is a mirror image of the front side. The garment part 1 comprises a torso portion 2, which is divided in two sides by a central longitudinal axis CLA. The central longitudinal axis CLA runs through a neckline 4 and a crotch 5. A leg 6 and a sleeve 7 are attached to the torso portion 2. There may be a seam 8 between the torso portion 2 and the sleeve 7. The sleeve 7 is attached to a shoulder section 3, which extends from the front side of the garment part 1 to the back side of the garment part 1. The shoulder section 3 comprises in Fig.3 a front piece and a back piece that are joined at the shoulder section 3. In Fig.3 there is a sleeve 7 but it is also possible that there is only an arm hole 9, i.e. the garment part 1 is sleeveless as shown in Fig.4.^It is also possible that the shoulder section 3 comprises at least one strap, which extends from the front side to the back side. The leg 6 and the shoulder section 3 are on the same side of the central longitudinal axis CLA. Figures 5a and 5b shows pieces of a garment part 1, i.e. a front side piece FS and a back side piece BS. The front side piece FS and the back side piece BS have the same pattern. Together with possible sleeves 7 they form the garment part 1. Figure 5c shows possible seams that are required to join the pieces FS and BS together. There is a first side seam 17, a second lower side seam 18, a sec- ond upper side seam 19 and a shoulder seam 20. Some of the seams may be omit- ted. For example, the first side seam 17 may be omitted if a fabric to be cut is folded so that there are two layers of the fabric one upon the other and the pieces FS, BS are cut in one go. According to another example, the first side seam 17 and the sec- ond upper side seam 19 may be omitted if the pieces FS, BS are cut from a tubular fabric of a suitable breadth. Figure 6 shows various alternatives of the garment part 1. The garment part 1 may be sleeveless as at 12, it may have a short sleeve as at 11, or it may have a long sleeve as at 10. The garment part 1 may have a short leg as at 13, it may have a medium-length leg as at 14, or a long leg as at 15. The garment part 1 may com- prise a bootee 16 integrated in the leg 6. All sleeve and leg combinations are possi- ble, i.e. there may be e.g. a garment part 1 having a short sleeve as at 11 and a long leg as at 15, or a garment part 1 having a long sleeve as at 10 and a short leg as at 13. Thus, a great number of various combinations are available. In connection with the short leg as at 13 the seam 18 is required in order to form a proper leg opening. Figure 7 shows garment parts 1, one marked by A (Fig.7a), one marked by B (Fig.7b), and one marked by C (Fig.7c). Fig.7 shows front views of the gar- ment parts 1 but they may as well be back views of the garment parts 1 since the garment parts 1 have identical patterns on the front and back sides, i.e. the shape of the front side piece is identical to the shape of the back side piece. The garment parts A, B and C comprise a neck opening 21 and a leg opening 22. The neck opening 21 is a diagonal opening that extends from the edge 23 of the shoulder section 3 to the opposite underarm 24 on both front and back side of the garment part 1. The leg opening 22 is a diagonal opening that extends from the hip 25 to the crotch 5 on both front and back side of the garment. Fig.7d shows the garment part A on top of the garment part B. Fig.7e shows the same garment parts as Fig.7d but in a different order. Fig.7f shows the garment parts A and B so that their back sides are turned to the front side and the part A is on top of the part B. Fig.7g shows the same garment parts A and B as Fig.7e but the part B is on top of the part A. It is possible to replace the garment part A or the garment part B by a garment part C of Fig. 7c or any other garment part 1. Thus, it is possible to get numerous outfits by using only a few garment parts 1. Figure 8 shows garment parts 1, one marked by D (Fig.8a), one marked by E (Fig.8b), and one marked by F (Fig.8c). Fig.8 shows front views of the gar- ment parts 1 but they may as well be back views of the garment parts 1 since the garment parts 1 have identical patterns on the front and back sides, i.e. the shape of the front side is identical to the shape of the back side. The garment parts D, E and F comprise a neck opening 21 and a leg opening 22. The neck opening 21 is a diagonal opening that extends from the edge 23 of the shoulder section 3 to the opposite underarm 24 on both front and back side of the garment part 1. The leg opening 22 is a diagonal opening that extends from the hip 25 to the crotch 5 on both front and back side of the garment. Fig.8d shows the garment part D on top of the garment part E. Fig. 8e shows the same garment parts as Fig. 8d but in a different order. Fig.8f shows the garment parts D and E so that their back sides are turned to the front side and the part D is on top of the part E. Fig.8g shows the same garment parts D and E as Fig.8e but the part E is on top of the part D. It is possible to replace the garment part D or the garment part E by a garment part F of Fig. 8c or any other garment part 1. Thus, it is possible to get numerous outfits in the same manner as in connection with Fig.7. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The inven- tion and its embodiments are not limited to the examples described above but may vary within the scope of the claims.