Function parse_boolean_atom 

fn parse_boolean_atom<T, U>(
    pair: Pair<'_, Rule>,
    builder: &U,
    ctx: &TLAParsingContext<'_>,
) -> Result<BooleanExpression<T>, Error>
where
    T: Atomic + 'static,
    U: IsDeclared<T> + IsDeclared<Parameter>,

Parse boolean_atom