bpy_extras submodule (bpy_extras.id_map_utils)

bpy_extras.id_map_utils.get_id_reference_map()

Return a dictionary of direct data-block references for every data-block in the blend file.

bpy_extras.id_map_utils.get_all_referenced_ids(id, ref_map)

Return a set of IDs directly or indirectly referenced by id.