code: def collapse(self, function):
          "Deprecated method to collapse layers in the Overlay."
          if config.future_deprecations:
              self.param.warning('Overlay.collapse is deprecated, to'
                                 'collapse multiple elements use a HoloMap.')
  
          elements = list(self)
          types = [type(el) for el in elements]
          values = [el.group for el in elements]
          if not len(set(types)) == 1 and len(set(values)) == 1:
              raise Exception("Overlay is not homogeneous in type or group "
                              "and cannot be collapsed.")
          else:
              return elements[0].clone(types[0].collapse_data([el.data for el in elements],
                                                              function, self.kdims)f collapse(self, function):
          "Deprecated method to collapse layers in the Overlay."
          if config.future_deprecations:
              self.param.warning('Overlay.collapse is deprecated, to'
                                 'collapse multiple elements use a HoloMap.')
  
          elements = list(self)
          types = [type(el) for el in elements]
          values = [el.group for el in elements]
          if not len(set(types)) == 1 and len(set(values)) == 1:
              raise Exception("Overlay is not homogeneous in type or group "
                              "and cannot be collapsed.")
          else:
              return elements[0].clone(types[0].collapse_data([el.data for el in elements],
                                                              function, self.kdims))
docs: Deprecated method to collapse layers in the Overlay.