code: public void initialize(int[] graphVertexDegrees) {
          log.info("Initializing: Creating Huffman tree and lookup table...");
          GraphHuffman gh = new GraphHuffman(graphVertexDegrees.length);
          gh.buildTree(graphVertexDegrees);
          lookupTable = new InMemoryGraphLookupTable(graphVertexDegrees.length, vectorSize, gh, learningRate);
          initCalled = true;
          log.info("Initialization complete");
      }
docs: Initialize the DeepWalk model with a list of vertex degrees for a graph.<br>
  Specifically, graphVertexDegrees[i] represents the vertex degree of the ith vertex<br>
  vertex degrees are used to construct a binary (Huffman) tree, which is in turn used in
  the hierarchical softmax implementation
  @param graphVertexDegrees degrees of each vertex