static contains(str, needle) {
        //TODO Use `Array.prototype.includes()` when available (cf. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes)
        if (!this.isString(str) || !this.isString(needle) || str === '' || needle === '') {
            return false;
        }

        return str.indexOf(needle) !== -1;
    }
Return `true` is the string `str` contains the string `needle`
Note: this function does not coerce the parameters types

@param {string} str
@param {string} needle
@returns {boolean}