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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _excerpt_step(n_samples, n_excerpts=None, excerpt_size=None):
 """Compute the step of an excerpt set as a function of the number of excerpts or their sizes."""

    assert n_excerpts >= 2
    step = max((n_samples - excerpt_size) // (n_excerpts - 1),
               excerpt_size)
    return step