'Call the ``prooftrans`` 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_prooftrans(self, input_str, args=[], verbose=False):

    if (self._prooftrans_bin is None):
        self._prooftrans_bin = self._find_binary('prooftrans', verbose)
    return self._call(input_str, self._prooftrans_bin, args, verbose)
