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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 _move_datetime(dt, direction, delta):
 """ Move datetime given delta by given direction """

    if direction == 'next':
        dt = dt + delta
    elif direction == 'last':
        dt = dt - delta
    else:
        pass
        # raise some delorean error here
    return dt