push() prepends the given message to an internal stack in the statusbar, along with its associated context_id. It is best to allow the statusbar to generate the context_id for itself, as the value can then change from one run to another to respond to the user's pattern of interaction with the application. Use get_context_id() to do this.

The returned value is a unique message_id, which is needed as a parameter in the remove() method. This is simply an incremented value, beginning at 1.

This method causes the "text-pushed" signal to be emitted.