code: def get_header_by_name(self, hdrname):
          '''
          Return the header object that has the given (string) header
          class name.  Returns None if no such header exists.
          '''
          for hdr in self._headers:
              if hdr.__class__.__name__ == hdrname:
                  return hdr
          return Nonf get_header_by_name(self, hdrname):
          '''
          Return the header object that has the given (string) header
          class name.  Returns None if no such header exists.
          '''
          for hdr in self._headers:
              if hdr.__class__.__name__ == hdrname:
                  return hdr
          return None
docs: Return the header object that has the given (string) header
          class name.  Returns None if no such header exists.