<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_output_every(dirname):
 """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. """

    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]