Returns a coma-separated list of method names that are allowed on
        this instance. Useful to set the ``Allowed`` response header.

def get_allowed_methods(self):
        """Returns a coma-separated list of method names that are allowed on
        this instance. Useful to set the ``Allowed`` response header.
        """
        return ", ".join([method for method in dir(self)
            if method.upper() == method
            and callable(getattr(self, method))])