code: def get_output_every(dirname):
      
      fnames = get_filenames(dirname)
      i_s = np.array([_f_to_i(fname) for fname in fnames])
      everys = list(set(np.diff(i_s)))
      if len(everys) > 1:
          raise TypeError('Multiple values for `output_every` '
                          'found, {}.'.format(everys))
      return everys[0]
docs: Get how many iterations between outputs have been done in a directory
      run.
  
      If there are multiple values used in a run, raise an exception.
  
      Parameters
      ----------
      dirname: str
          A path to a directory.
  
      Returns
      -------
      output_every: int
          The inferred number of iterations between outputs.
  
      Raises
      ------
      TypeError
          If there are multiple different values for `output_every` found. This
          usually means a run has been resumed with a different value.