The ornamental design for a pump, as shown and described.
FIG. 1 is a perspective view of an embodiment of a pump embodying my design;
FIG. 2 is a front view of the pump of FIG. 1;
FIG. 3 is a first side view of the pump of FIG. 1;
FIG. 4 is a second side view of the pump of FIG. 1;
FIG. 5 is a rear view of the pump of FIG. 1;
FIG. 6 is a top view of the pump of FIG. 1; and,
FIG. 7 is a bottom view of the pump of FIG. 1.
The scale shown in the drawings is for illustrative purposes only and forms no part of the claimed design. Additionally, the broken lines shown herein are included for the purpose of illustrating an environment of the article and form no part of the claimed design.