code: def truncate(self, new_count):
          
          self.posterior_state_estimates = self.posterior_state_estimates[:new_count]
          self.prior_state_estimates = self.prior_state_estimates[:new_count]
          self.measurements = self.measurements[:new_count]
          self.process_matrices = self.process_matrices[:new_count]
          self.process_covariances = self.process_covariances[:new_count]
docs: Truncate the filter as if only *new_count* :py:meth:`.predict`,
          :py:meth:`.update` steps had been performed. If *new_count* is greater
          than :py:attr:`.state_count` then this function is a no-op.
  
          Measurements, state estimates, process matrices and process noises which
          are truncated are discarded.
  
          Args:
              new_count (int): Number of states to retain.