def METHOD_NAME(self) -> float:
    """A maximum on the trace distance between `val`'s input and output.
    Generally this method is used when deciding whether to keep gates, so
    only the behavior near 0 is important. Approximations that overestimate
    the maximum trace distance are permitted. If, for any case, the bound
    exceeds 1, this function will return 1.  Underestimates are not
    permitted.
    """