code: def test_sort_key(self):
      self.run_test(
          "def sort_key(n):\n b=[(1,3),(5,4),(2,n)]\n b.sort(key=lambda x: x[1])\n return b",
          1,
          sort_key=[int],
      )
  
imports: from pythran.tests import TestEnv
  from pythran.typing import List, NDArray
  import numpy
label_desc: Use image node_id 15 for calling the TestList obj's underlying member method code with example usage: obj.test_sort_key() without return types