docs: def _fill_lookup_prop(self, requirements_properties):
          """Fills the polarion-lookup-method property."""
          if not self._lookup_prop:
              raise Dump2PolarionException("Failed to set the 'polarion-lookup-method' property")
  
          etree.SubElement(
              requirements_properties,
              "property",
              {"name": "lookup-method", "value": self._lookup_prop},
          )