Method non_zero_length

cpp/src/arrow/sparse_tensor.h:293–293

\brief Return the number of non zero values in the sparse tensor related to this sparse index

  /// \brief Return the number of non zero values in the sparse tensor related
  /// to this sparse index
  int64_t non_zero_length() const override { return indices_->shape()[0]; }

  /// \brief Return a string representation of the sparse index
  std::string ToString() const override {