    /**
     * Searches for an element that matches the conditions defined by the specified predicate, and returns 
     * an Observable sequence with the zero-based index of the first occurrence within the entire Observable sequence. 
     * @param {Function} predicate The predicate that defines the conditions of the element to search for.
     * @param {Any} [thisArg] Object to use as `this` when executing the predicate.          
     * @returns {Observable} An Observable sequence with the zero-based index of the first occurrence of an element that matches the conditions defined by match, if found; otherwise, –1.
    */
    observableProto.findIndex = function (predicate, thisArg) {
        return findValue(this, predicate, thisArg, true);
    };
