The ornamental design for a topportion of a vehicle, as shown and described.
FIG. 1 is a right, front perspective view of a top portion of a vehicle showing my new design;
FIG. 2 is a left, front perspective view thereof;
FIG. 3 is a left, rear perspective view thereof;
FIG. 4 is a right, rear perspective view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a left side view thereof;
FIG. 8 is a right side view thereof; and,
FIG. 9 is a top view thereof.
The portions of the vehicle shown throughout the drawing views in de-emphasized and half-tone portions outside the broken lines and the broken lines representing the boundary and configuration of what is claimed as the design are for environmental and illustrative purposes only and form no part of the claimed design.