code: def entries(self):
          
          # We use DataFrames for serialization of MatrixEntry entries
          # from Java, so we first convert the RDD of entries to a
          # DataFrame on the Scala/Java side. Then we map each Row in
          # the DataFrame back to a MatrixEntry on this side.
          entries_df = callMLlibFunc("getMatrixEntries", self._java_matrix_wrapper._java_model)
          entries = entries_df.rdd.map(lambda row: MatrixEntry(row[0], row[1], row[2]))
          return entries
docs: Entries of the CoordinateMatrix stored as an RDD of
          MatrixEntries.
  
          >>> mat = CoordinateMatrix(sc.parallelize([MatrixEntry(0, 0, 1.2),
          ...                                        MatrixEntry(6, 4, 2.1)]))
          >>> entries = mat.entries
          >>> entries.first()
          MatrixEntry(0, 0, 1.2)