code: def _convert_labeled_point_to_libsvm(p):
          
          from pyspark.mllib.regression import LabeledPoint
          assert isinstance(p, LabeledPoint)
          items = [str(p.label)]
          v = _convert_to_vector(p.features)
          if isinstance(v, SparseVector):
              nnz = len(v.indices)
              for i in xrange(nnz):
                  items.append(str(v.indices[i] + 1) + ":" + str(v.values[i]))
          else:
              for i in xrange(len(v)):
                  items.append(str(i + 1) + ":" + str(v[i]))
          return " ".join(items)
docs: Converts a LabeledPoint to a string in LIBSVM format.