The ornamental design for a pattern for containers, as shown and described.
FIG. 1 is a front perspective view of a pattern for containers in accordance with the present design without a claim to a specific shape to which the pattern may be applied thereof;
FIG. 2 is a top plan view thereof;
FIG. 3 is a right side elevational view thereof, the left side elevational view being a mirror image thereof;
FIG. 4 is a front elevational view thereof, the rear side elevational view being a mirror image thereof; and,
FIG. 5 is an enlarged detail view of area 5 circumscribed within FIG. 1.
The broken lines shown in the drawings illustrate portions of the pattern for containers that form no part of the claimed design.