update transtree to be compatible with networkx 2.6
@@ -1539,6 +1539,7 @@ class TransTree(Analyzer):
# Next, add edges from linelist
for edge in people.infection_log:
+ if edge['source'] is not None: # Skip seed infections
self.graph.add_edge(edge['source'],edge['target'],date=edge['date'],layer=edge['layer'])
return
