<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _before_after(n_samples):
 """Get the number of samples before and after."""

    if not isinstance(n_samples, (tuple, list)):
        before = n_samples // 2
        after = n_samples - before
    else:
        assert len(n_samples) == 2
        before, after = n_samples
        n_samples = before + after
    assert before >= 0
    assert after >= 0
    assert before + after == n_samples
    return before, after