docs: def _parse_protein_tag(self):
          '''Parses the protein tag to get the names and EC numbers.'''
  
          protein_nodes = self._dom.getElementsByTagName('protein')
          assert(len(protein_nodes) == 1)
          self.protein_node = protein_nodes[0]
  
          self._get_recommended_name()
          self._get_submitted_names()
          self._get_alternative_names()