def buildSubgraph(parent, name, readable_name=None):
if isinstance(parent, EDSMRootModel):
parent = parent.states
subgraph = SubElement(parent,
u"{%s}subgraph" % EDSM_NAMESPACE_URI,
name=name)
if readable_name:
subgraph.readable_name = readable_name
subgraph.id = uniqueID(parent, str(id(subgraph)))
states = subgraph.states
subgraph.entry_state = buildState(states, 'entry')
subgraph.exit_state = buildState(states, 'exit')
return subgraph
