Interface portion of a pump

The design consists of the shape, configuration, pattern and ornamentation of the portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT shown in the drawings, of which: FIG. 1 is a perspective view of an embodiment of our design for an interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT, with a lock member in an open position;FIG. 2 is a front view of the interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT of FIG. 1;FIG. 3 is a rear view of the interface portion of the pump of FIG. 1;FIG. 4 is a left side view of the interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT of FIG. 1;FIG. 5 is a right side view of the interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT of FIG. 1;FIG. 6 is a top view of the interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT of FIG. 1; andFIG. 7 is a bottom view of the interface portion of the PUMP FOR DELIVERING A BENEFICIAL AGENT of FIG. 1.The stippled lines of the drawings are for illustrative purposes only and do not fom part of the design. The bold, wavy lines do not constitute a feature of the design, but are included for illustrative purposes only in order to define the boundary of the design.