code: def charge(self):
          
          if self._reader._level == 3:
              # Look for FBC charge
              for ns in (FBC_V2, FBC_V1):
                  charge = self._root.get(_tag('charge', ns))
                  if charge is not None:
                      return self._parse_charge_string(charge)
          else:
              charge = self._root.get('charge')
              if charge is not None:
                  return self._parse_charge_string(charge)
  
          return None
docs: Species charge