code: def _ParseFValue(self, registry_key):
      
      registry_value = registry_key.GetValueByName('F')
      if not registry_value:
        raise errors.ParseError(
            'missing value: "F" in Windows Registry key: {0:s}.'.format(
                registry_key.name))
  
      f_value_map = self._GetDataTypeMap('f_value')
  
      try:
        return self._ReadStructureFromByteStream(
            registry_value.data, 0, f_value_map)
      except (ValueError, errors.ParseError) as exception:
        raise errors.ParseError(exception)
docs: Parses an F value.
  
      Args:
        registry_key (dfwinreg.WinRegistryKey): Windows Registry key.
  
      Returns:
        f_value: F value stored in the Windows Registry key.
  
      Raises:
        ParseError: if the Windows Registry key does not contain an F value or
            F value cannot be parsed.