code: def _make_ring(n):
      # from lobpcg scipy tests
      col = np.zeros(n)
      col[1] = 1
      A = sla.toeplitz(col)
      D = np.diag(A.sum(axis=1))
      L = D - A
      # Compute the full eigendecomposition using tricks, e.g.
      # http://www.cs.yale.edu/homes/spielman/561/2009/lect02-09.pdf
      tmp = np.pi * np.arange(n) / n
      analytic_w = 2 * (1 - np.cos(tmp))
      analytic_w.sort()
      analytic_w = analytic_w[::-1]
  
      return L, analytic_w
  
imports: import functools
  import re
  import os
  import unittest
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  import scipy.linalg
  import scipy.sparse
  import jax
  from jax import config
  from jax._src import test_util
  from jax.experimental.sparse import linalg, bcoo
  import jax.numpy
label_desc: Use image node_id 4 for calling a global function with example usage: _make_ring(n) and returns: L,  analytic_w