def sparse_matrix_indices(spmat):
    """Return the indices of the given sparse matrix.

    Parameters
    ----------
    spmat : SparseMatrix
        The framework-specific sparse matrix.

    Returns
    -------
    index : tuple
        This is used to support different sparse formats.
        For COO format:
          index=('coo', coord), where coord is of shape (2, nnz).
          coord[0,:] should be the row index and coord[1,:] should be
          the column index.
        For CSR format:
          index=('csr', indices, indptr), where indices is of shape (nnz,)
          and indptr is of shape (nrows+1,). See ``scipy.sparse.csr_matrix``
          for more documents on what each array means.
    """
    pass
