def _detuplify_version(input_tuple):
    """
    Coerces the version tuple (if not None), to a version string.
    Ex. (1, 7, 0) becomes "1.7.0".
    """
    if input_tuple is None:
        return ""
    assert isinstance(input_tuple, tuple)
    string = ".".join(str(number) for number in input_tuple)
    return string