docs: 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