Function require_that 

pub fn require_that<T, F>(
    value: T,
    path: &str,
    predicate: F,
    code: &str,
    message: &str,
) -> ArgumentResult<T>
where
    F: FnOnce(&T) -> bool,

Validates a value with a caller-provided predicate.

The predicate receives a shared reference to value. If it returns true, this function returns the original value without cloning it or allocating error strings. If it returns false, path, code, and message identify the failed validation rule.

Errors

Returns ArgumentErrorKind::Custom when predicate returns false. The error owns copies of path, code, and message.