code: def Expand(self, macro_ref_str):
      
      match = _MACRO_RE.match(macro_ref_str)
      if match is None or match.group(0) != macro_ref_str:
        raise PDDMError('Failed to parse macro reference: "%s"' % macro_ref_str)
      if match.group('name') not in self._macros:
        raise PDDMError('No macro named "%s".' % match.group('name'))
      return self._Expand(match, [], macro_ref_str)
docs: Expands the macro reference.
  
      Args:
        macro_ref_str: String of a macro reference (i.e. foo(a, b)).
  
      Returns:
        The text from the expansion.
  
      Raises:
        PDDMError if there are any issues.