directedGraph.putEdge(N1, N2);
    directedGraph.putEdge(N2, N1);
    directedGraph.putEdge(N1, N3); // only incident to one node in nodeSubset
    directedGraph.putEdge(N4, N4);
    directedGraph.putEdge(5, 6); // not incident to any node in nodeSubset

    MutableGraph<Integer> expectedSubgraph = GraphBuilder.directed().allowsSelfLoops(true).build();
    expectedSubgraph.putEdge(N1, N2);

    directedGraph.putEdge(N1, N2);
    directedGraph.putEdge(N2, N1);
    directedGraph.putEdge(N1, N3); // only incident to one node in nodeSubset
    directedGraph.putEdge(N4, N4);
    directedGraph.putEdge(5, 6); // not incident to any node in nodeSubset

    MutableGraph<Integer> expectedSubgraph = GraphBuilder.directed().allowsSelfLoops(true).build();
    expectedSubgraph.putEdge(N1, N2);

   * self-loops twice (equivalently, the number of times an edge touches {@code node}).
   *
   * <p>For directed networks, this is equal to {@code inDegree(node) + outDegree(node)}.
   *
   * <p>For undirected networks, this is equal to {@code incidentEdges(node).size()} + (number of
   * self-loops incident to {@code node}).
   *

  /**
   * Returns the count of {@code node}'s incident edges, counting self-loops twice (equivalently,
   * the number of times an edge touches {@code node}).
   *
   * <p>For directed graphs, this is equal to {@code inDegree(node) + outDegree(node)}.
   *
   * <p>For undirected graphs, this is equal to {@code incidentEdges(node).size()} + (number of
   * self-loops incident to {@code node}).
   *

  /**
   * Returns the count of {@code node}'s incident edges, counting self-loops twice (equivalently,
   * the number of times an edge touches {@code node}).
   *
   * <p>For directed graphs, this is equal to {@code inDegree(node) + outDegree(node)}.
   *
   * <p>For undirected graphs, this is equal to {@code incidentEdges(node).size()} + (number of
   * self-loops incident to {@code node}).
   *

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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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      unless required by applicable law (such as deliberate and grossly
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      liable to You for damages, including any direct, indirect, special,
      incidental, or consequential damages of any character arising as a
      result of this License or out of the use or inability to use the
      Work (including but not limited to damages for loss of goodwill,

   negligence), contract, or otherwise, shall any Contributor, or anyone who
   distributes Covered Software as permitted above, be liable to You for any
   direct, indirect, special, incidental, or consequential damages of any
   character including, without limitation, damages for lost profits, loss of
   goodwill, work stoppage, computer failure or malfunction, or any and all

LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

   negligence), contract, or otherwise, shall any Contributor, or anyone who
   distributes Covered Software as permitted above, be liable to You for any
   direct, indirect, special, incidental, or consequential damages of any
   character including, without limitation, damages for lost profits, loss of
   goodwill, work stoppage, computer failure or malfunction, or any and all