Convenience method for passing a string through a pipeline and
        getting strings out. This method takes care of wrapping the passed
        string in a token and mapping the resulting tokens back to strings.

def run_string(self, string, metadata=None):
        """Convenience method for passing a string through a pipeline and
        getting strings out. This method takes care of wrapping the passed
        string in a token and mapping the resulting tokens back to strings."""
        token = Token(string, metadata)
        return [str(tkn) for tkn in self.run([token])]