def add_to_configs(self, configs):
        """Add one or more measurement configurations to the stored
        configurations

        Parameters
        ----------
        configs: list or numpy.ndarray
            list or array of configurations

        Returns
        -------
        configs: Kx4 numpy.ndarray
            array holding all configurations of this instance
        """
        if len(configs) == 0:
            return None

        if self.configs is None:
            self.configs = np.atleast_2d(configs)
        else:
            configs = np.atleast_2d(configs)
            self.configs = np.vstack((self.configs, configs))
        return self.configs
Add one or more measurement configurations to the stored
        configurations

        Parameters
        ----------
        configs: list or numpy.ndarray
            list or array of configurations

        Returns
        -------
        configs: Kx4 numpy.ndarray
            array holding all configurations of this instance