The ornamental design for a collectionbag, as shown and described.
FIG. 1 is a perspective view of a collection bag, showing the new design.
FIG. 2 is a front elevational view of FIG. 1.
FIG. 3 is a rear elevational view of FIG. 1.
FIG. 4 is a right side elevational view of FIG. 1, the left side thereof being a mirror image.
FIG. 5 is a bottom plan view of FIG. 1; and,
FIG. 6 is a top plan view of FIG. 1.
The broken line showing of portions of the collection bag is included for the purpose of illustrating environmental structure and forms no part of the claimed design.