+ "that allows parallel edges, call allowsParallelEdges(true) on the Builder.";
  static final String SELF_LOOPS_NOT_ALLOWED =
      "Cannot add self-loop edge on node %s, as self-loops are not allowed. To construct a graph "
          + "that allows self-loops, call allowsSelfLoops(true) on the Builder.";
  static final String NOT_AVAILABLE_ON_UNDIRECTED =
      "Cannot call source()/target() on a EndpointPair from an undirected graph. Consider calling "

	}
}

// Borrowed from mutex_test.go
func HammerMutex(m *DRWMutex, loops int, cdone chan bool) {
	for range loops {
		m.Lock(id, source)
		m.Unlock(context.Background())
	}
	cdone <- true
}

// Borrowed from mutex_test.go
func TestMutex(t *testing.T) {
	loops := 200
	if testing.Short() {
		loops = 5
	}
	c := make(chan bool)
	m := NewDRWMutex(ds, "test")
	for range 10 {

    protected final BufferedReader reader;

    /** The line that has been read */
    protected String line = EMPTY;

    /**
     * Returns an {@link Iterable} that wraps a {@link LineIterator} for use in enhanced for-loops.
     *
     * @param reader
     *            The {@link Reader} to read strings from. Must not be {@literal null}.
     * @return An {@link Iterable} that wraps a {@link LineIterator}.
     */

  /**
   * 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}).
   *

 * user-defined properties.
 *
 * <p>A {@code Graph} built by this class has the following default properties:
 *
 * <ul>
 *   <li>does not allow self-loops
 *   <li>orders {@link Graph#nodes()} in the order in which the elements were added (insertion
 *       order)
 * </ul>
 *
 * <p>{@code Graph}s built by this class also guarantee that each collection-returning accessor

  /**
   * 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}).
   *

        }
        if (!advance()) {
          return endOfData();
        }
      }
    }
  }

  /**
   * If the graph is undirected, each unordered [node, otherNode] pair (except self-loops) will be
   * visited twice if there is an edge connecting them. To avoid returning duplicate {@link
   * EndpointPair}s, we keep track of the nodes that we have visited. When processing endpoint

    }
    throw new IllegalArgumentException("Unrecognized strategy: " + strategy);
  }

  /**
   * A strategy for adding self-loops to {@linkplain #transitiveClosure(Graph,
   * TransitiveClosureSelfLoopStrategy) the transitive closure graph}. All strategies preserve
   * self-loops that are present in the original graph.
   *
   * <p>The strategies differ based on how they define "cycle incident to a node".
   *

 * with user-defined properties.
 *
 * <p>A {@code ValueGraph} built by this class has the following default properties:
 *
 * <ul>
 *   <li>does not allow self-loops
 *   <li>orders {@link ValueGraph#nodes()} in the order in which the elements were added (insertion
 *       order)
 * </ul>
 *

  /**
   * 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}).
   *