I claim the ornamental design for a bag, as shown and described.
FIG. 1 is a front perspective view of a bag of the claimed design;
FIG. 2 is a front elevational view of the bag shown in FIG. 1;
FIG. 3 is a rear elevational view of the bag shown in FIG. 1;
FIG. 4 is a right side elevational view of the bag shown in FIG. 1;
FIG. 5 is a left side elevational view of the bag shown in FIG. 1;
FIG. 6 is a top plan view of the bag shown in FIG. 1; and,
FIG. 7 is a bottom plan view of the bag shown in FIG. 1.
The claimed design is shown in the figures by solid lines as well as by dashed lines that represent stitching. The dot-dashed lines shown in FIG. 6 are for illustrative purposes only and form no part of the claimed design.