the location identifying the dataset.
the GQuark id to identify the data element.
the data element.
the function to call when the data element is removed. This function will be called with the data element and can be used to free any memory allocated for it.
Sets the data element associated with the given GQuark id, and also the function to call when the data element is destroyed. Any previous data with the same key is removed, and its destroy function is called.