docs: private void pop(char c) throws JSONException {
      if (this.top <= 0) {
        throw new JSONException("Nesting error.");
      }
      char m = this.stack[this.top - 1] == null ? 'a' : 'k';
      if (m != c) {
        throw new JSONException("Nesting error.");
      }
      this.top -= 1;
      this.mode = this.top == 0 ? 'd' : this.stack[this.top - 1] == null ? 'a' : 'k';
    }