code: def _validate_value(self, proposal):
          "Replace all values with the actual objects in the options list"
          try:
              return tuple(findvalue(self._options_values, i, self.equals) for i in proposal.value)
          except ValueError:
              raise TraitError('Invalid selection: value not found'f _validate_value(self, proposal):
          "Replace all values with the actual objects in the options list"
          try:
              return tuple(findvalue(self._options_values, i, self.equals) for i in proposal.value)
          except ValueError:
              raise TraitError('Invalid selection: value not found')
docs: Replace all values with the actual objects in the options list