code: public static DMatrixSparseCSC transpose(DMatrixSparseCSC a , @Nullable DMatrixSparseCSC a_t , @Nullable IGrowArray gw ) {
  
          if( a_t == null ) {
              a_t = new DMatrixSparseCSC(a.numCols,a.numRows,a.nz_length);
          } else {
              a_t.reshape(a.numCols,a.numRows,a.nz_length);
          }
  
          ImplCommonOps_DSCC.transpose(a, a_t, gw);
          return a_t;
      }
docs: Perform matrix transpose
  
  @param a Input matrix.  Not modified
  @param a_t Storage for transpose of 'a'.  Must be correct shape.  data length might be adjusted.
  @param gw (Optional) Storage for internal workspace.  Can be null.
  @return The transposed matrix