findNeutralCharacter() {
        if (!this._neutralCharacterSearched) {
            this._neutralCharacterSearched = true;
            if (!this._neutralCharacter) {
                this._neutralCharacter = this._findNeutralCharacterInRange(48 /* CharCode.Digit0 */, 57 /* CharCode.Digit9 */);
            }
            if (!this._neutralCharacter) {
                this._neutralCharacter = this._findNeutralCharacterInRange(97 /* CharCode.a */, 122 /* CharCode.z */);
            }
            if (!this._neutralCharacter) {
                this._neutralCharacter = this._findNeutralCharacterInRange(65 /* CharCode.A */, 90 /* CharCode.Z */);
            }
        }
        return this._neutralCharacter;
    }
Find a character in the range [0-9a-zA-Z] that does not appear in the open or close