code: def has_header_line(self, key, id_):
          
          if key not in self._indices:
              return False
          else:
              return id_ in self._indices[key]
docs: Return whether there is a header line with the given ID of the
          type given by ``key``
  
          :param key: The VCF header key/line type.
          :param id_: The ID value to compare fore
  
          :return: ``True`` if there is a header line starting with ``##${key}=``
              in the VCF file having the mapping entry ``ID`` set to ``id_``.