code: private Matrix getEdgeSimMatrix(List<Edge> edgeList, SparseMatrix sm,
                                      boolean keepSimilarityMatrixInMemory) {
          return (keepSimilarityMatrixInMemory) 
              ? calculateEdgeSimMatrix(edgeList, sm)
              : new LazySimilarityMatrix(edgeList, sm);            
      }
docs: Returns the edge similarity matrix for the edges in the provided sparse
  matrix.