<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_node(self, id, label=None, type='CLASS', meta=None):
 """ Add a new node to the ontology """

        g = self.get_graph()
        if meta is None:
            meta={}
        g.add_node(id, label=label, type=type, meta=meta)