  JsonDocument() {
    assert(s_pActiveDocument ==
           nullptr);  // When using default allocator, only one document can be
                      // active at a time, if you need multiple active at once,
                      // define TINYGLTF_USE_RAPIDJSON_CRTALLOCATOR
    s_pActiveDocument = this;
  }
  JsonDocument() {
    assert(s_pActiveDocument ==
           nullptr);   
                       
                       
    s_pActiveDocument = this;
  }