'Call the ``interpformat`` binary with the given input.
:param input_str: A string whose contents are used as stdin.
:param args: A list of command-line arguments.
:return: A tuple (stdout, returncode)
:see: ``config_prover9``'

def _call_interpformat(self, input_str, args=[], verbose=False):

    if (self._interpformat_bin is None):
        self._interpformat_bin = self._modelbuilder._find_binary('interpformat', verbose)
    return self._modelbuilder._call(input_str, self._interpformat_bin, args, verbose)
