code: def _flatten_obs(self, obs_dict, verbose=False):
          
          ob_lst = []
          for key in obs_dict:
              if key in self.keys:
                  if verbose:
                      print("adding key: {}".format(key))
                  ob_lst.append(obs_dict[key])
          return np.concatenate(ob_lst)
docs: Filters keys of interest out and concatenate the information.
  
          Args:
              obs_dict: ordered dictionary of observations