The ornamental design for a sewingmachine, as shown and described.
FIG. 1 is a perspective view of a sewing machine;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right-side view thereof;
FIG. 5 is a left-side view thereof; and,
FIG. 6 is a rear view thereof.
The broken lines depict environmental subject matter only and form no part of the claimed design. The bottom view depicts unclaimed subject matter only and thus is not shown.