def push_func(self, cuin, callback):
        """Push a function for dfp.

        :param cuin: str,unicode: Callback Unique Identifier Name.

        :param callback: callable: Corresponding to the cuin to perform a function.

        :raises: DFPError,NotCallableError: raises an exception

        .. versionadded:: 2.3.0
        """
        if cuin and isinstance(cuin, string_types) and callable(callback):
            if cuin in self._dfp_funcs:
                raise DFPError("The cuin already exists")
            else:
                self._dfp_funcs[cuin] = callback
        else:
            if not callable(callback):
                raise NotCallableError("The cuin %s cannot be called back" % cuin)
            raise DFPError("Invalid parameter")
Push a function for dfp.

        :param cuin: str,unicode: Callback Unique Identifier Name.

        :param callback: callable: Corresponding to the cuin to perform a function.

        :raises: DFPError,NotCallableError: raises an exception

        .. versionadded:: 2.3.0