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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 is_byte_range_valid(start, stop, length):
 """Checks if a given byte content range is valid for the given length. .. versionadded:: 0.7 """

    if (start is None) != (stop is None):
        return False
    elif start is None:
        return length is None or length >= 0
    elif length is None:
        return 0 <= start < stop
    elif start >= stop:
        return False
    return 0 <= start < length