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 unclaimed portions of the sewing machine and form no part of the claimed design. The shaded portion on the top of the sewing machine is intended to illustrate a color contrast with the remainder of the sewing machine.