Hi!
I'm having problems wrapping my head around this behaviour:
g = gt.Graph()
g.add_vertex()
g.vp['name_num'] = g.new_vp('object')
print(g.vp.name_num[0]) # None
g.vp.name_num[0] = [('a', 1)]
print(g.vp.name_num[0]) # [('a', 1)]
g.vp.name_num[0] = g.vp.name_num[0].append(('b', 2))
print(g.vp.name_num[0]) # None