Dear all, could you tell me what I am doing wrong in the following script, trying to filter an edge?

Best,

F.

bug.py:
import graph_tool as gt
_g = gt.Graph()
_g.add_vertex(2)
_g.add_edge(0,1)
print _g

_p = _g.new_edge_property('int')
for _e in _g.edges() : _p[_e] = 0

_g.set_edge_filter(_p)
print _g

[Flavien@localhost Downloads]$ python bug.py
<Graph object, directed, with 2 vertices and 1 edge at 0x256b990>
Traceback (most recent call last):
  File "bug.py", line 11, in <module>
    print _g
  File "/usr/lib/python2.7/site-packages/graph_tool/__init__.py", line 1272, in __repr__
    n = self.num_vertices()
  File "/usr/lib/python2.7/site-packages/graph_tool/__init__.py", line 2048, in num_vertices
    return self.__graph.GetNumberOfVertices()
RuntimeError: Vertex filter is active but edge filter is not. This is a bug.