code: def transpose(self):
          
          java_transposed_matrix = self._java_matrix_wrapper.call("transpose")
          return BlockMatrix(java_transposed_matrix, self.colsPerBlock, self.rowsPerBlock)
docs: Transpose this BlockMatrix. Returns a new BlockMatrix
          instance sharing the same underlying data. Is a lazy operation.
  
          >>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
          ...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
          >>> mat = BlockMatrix(blocks, 3, 2)
  
          >>> mat_transposed = mat.transpose()
          >>> mat_transposed.toLocalMatrix()
          DenseMatrix(2, 6, [1.0, 4.0, 2.0, 5.0, 3.0, 6.0, 7.0, 10.0, 8.0, 11.0, 9.0, 12.0], 0)