code: def test_davidson():
      from deepchem.utils.differentiation_utils.symeig import davidson
      from deepchem.utils.differentiation_utils import LinearOperator
  
      A = LinearOperator.m(torch.rand(2, 2))
      neig = 2
      mode = "lowest"
      eigen_val, eigen_vec = davidson(A, neig, mode)
      assert eigen_val.shape == torch.Size([2])
      assert eigen_vec.shape == torch.Size([2, 2])
  
imports: import pytest
label_desc: Use image node_id 29 for calling a global function with example usage: test_davidson() without return types