code: def test_branch_cut(self):
      assert np.isnan(sc.exp1(-1))
      assert sc.exp1(complex(-1, 0)).imag == (
          -sc.exp1(complex(-1, -0.0)).imag
      )
  
      assert_allclose(
          sc.exp1(complex(-1, 0)),
          sc.exp1(-1 + 1e-20j),
          atol=0,
          rtol=1e-15,
      )
      assert_allclose(
          sc.exp1(complex(-1, -0.0)),
          sc.exp1(-1 - 1e-20j),
          atol=0,
          rtol=1e-15,
      )
  
file_path: scipy/scipy/special/tests/test_exponential_integrals.py
imports: import pytest
  import numpy
  from numpy.testing import assert_allclose
  import scipy.special
label_desc: Use image node_id 1 for calling the TestExp1 obj's underlying member method code with example usage: obj.test_branch_cut() without return types