code: def delete_rows_csr(mat, indices):
      
      if not isinstance(mat, scipy.sparse.csr_matrix):
          raise ValueError("works only for CSR format -- use .tocsr() first")
      indices = list(indices)
      mask = np.ones(mat.shape[0], dtype=bool)
      mask[indices] = False
      return mat[mask]
docs: Remove the rows denoted by ``indices`` form the CSR sparse matrix ``mat``.