@staticmethod
def _req_spec_msg_to_str(msg):
    """
        Inverse of :meth:`Python._req_spec_to_msg`.

        Parameters
        ----------
        msg : PythonRequirementEnvironmentBlob

        Returns
        -------
        req_spec : str

        """
    return '{}{}{}'.format(msg.library, msg.constraint, '{}.{}.{}{}'.format
        (msg.version.major, msg.version.minor, msg.version.patch, msg.
        version.suffix))
