Directed Graph Edit Distance computation problem

[Heapflow]

Issue Description:
Graphs: I am comparing pairs of identical directed graphs represented in GXL format. Since the graphs are identical, I expect the GED to be 0.
Example Graph:

<gxl>
  <graph id="418" edgeids="false" edgemode="directed">
    <node id="0" />
    <node id="1" />
    <node id="2" />
    <node id="3" />
    <node id="4" />
    <node id="5" />
    <node id="6" />
    <node id="7" />
    <node id="8" />
    <node id="9" />
    <edge from="0" to="1" />
    <edge from="0" to="3" />
    <edge from="0" to="5" />
    <edge from="0" to="9" />
    <edge from="1" to="2" />
    <edge from="2" to="7" />
    <edge from="3" to="4" />
    <edge from="4" to="7" />
    <edge from="6" to="8" />
    <edge from="6" to="7" />
  </graph>
</gxl>

Observed Behavior: When I compute the GED using the AStar algorithm with the parameter undirected=0, the resulting GED is not 0 as expected.

Questions:

Data Validation: Is there a possibility that my directed graph data has an issue that affects the GED computation?
Toolkit Functionality: Could there be a bug or limitation in how the toolkit handles directed graphs, especially when using the AStar algorithm with undirected=0?