code: def expand_compositor_keys(cls, spec):
          
          expanded_spec={}
          applied_keys = []
          compositor_defs = {el.group:el.output_type.__name__
                             for el in Compositor.definitions}
          for key, val in spec.items():
              if key not in compositor_defs:
                  expanded_spec[key] = val
              else:
                  # Send id to Overlays
                  applied_keys = ['Overlay']
                  type_name = compositor_defs[key]
                  expanded_spec[str(type_name+'.'+key)] = val
          return expanded_spec, applied_keys
docs: Expands compositor definition keys into {type}.{group}
          keys. For instance a compositor operation returning a group
          string 'Image' of element type RGB expands to 'RGB.Image'.