def filter_graph(self):
        deleted_vert_ids = set()
        keys = list(self._vertices.keys())
        for text in keys:
            vertice = self._vertices[text]
            if len(vertice.datetimes) < 10:
                deleted_vert_ids.add(vertice.id)
                del self._vertices[text]
        for id1, id2 in self._edges:
            if id1 in deleted_vert_ids or id2 in deleted_virt_ids:
                del self._edges[(id1, id2)]

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-206-8d26d1279ae4> in <module>()
----> 1 graph_alt.filter_graph()

<ipython-input-203-117dd3824282> in filter_graph(self)
     25                 del self._vertices[text]
     26         for id1, id2 in self._edges:
---> 27             if id1 in deleted_vert_ids or id2 in deleted_virt_ids:
     28                 del self._edges[(id1, id2)]

NameError: name 'deleted_virt_ids' is not defined