I claim the ornamental design for a bag, as shown and described.
FIG. 1 is a Perspective view of a bag showing my new design;
FIG. 2 is a Front view of the bag as shown in FIG. 1;
FIG. 3 is a Back view of the bag as shown in FIG. 1;
FIG. 4 is a Right-side view of the bag as shown in FIG. 1;
FIG. 5 is a Left-side view of the bag as shown in FIG. 1;
FIG. 6 is a Top view of the bag as shown in FIG. 1; and,
FIG. 7 is a Bottom view of the bag as shown in FIG. 1.
The broken lines showing stitching, moveable zipper pulls, and zipper pathway are for illustrating portions of the bag and form no part of the claimed design. The moveable zipper pulls are shown in different positions to allow for the complete claimed design to be visible.