Function weighted
fn weighted<T: Strategy, impl Into<Probability>: Into<Probability>>(probability_of_some: impl Into<Probability>, t: T) -> OptionStrategy<T>
Return a strategy producing Optional values wrapping values from the
given delegate strategy.
Some values shrink to None.
Some is chosen with a probability given by probability_of_some, which
must be between 0.0 and 1.0, both exclusive.