[Bug]: `pattern.draw` fails to find flow or flow

[matulni]

Bug description
The method Pattern.draw_graph fails to find a flow on a pattern transpiled from circuit if the parameter flow_from_pattern is set to True (default behaviour).

If flow_from_pattern == False, the flow search is done on the underlying open graph and the function correctly finds a flow.

To Reproduce

from graphix.transpiler import Circuit
circuit = Circuit(2)
circuit.cnot(0, 1)
pattern = circuit.transpile().pattern
pattern.standardize()
print(pattern) # X(3,{2}) Z(0,{1}) Z(3,{1}) M(2) M(1) E(1,2) E(2,3) E(0,2) N(3) N(2)
pattern.draw_graph() # The pattern is not consistent with flow or gflow structure.
pattern.draw_graph(flow_from_pattern=False) # Flow detected in the graph.

Additional comments

This issue goes back at least to 73bac1f (unable to find a particular commit which might have broken this functionality).