code: def test_rvalue_readline(self):
      self.tempfile()
      self.run_test(
          "def _rvalue_readline(filename):\n return open(filename).readline()",
          self.filename,
          _rvalue_readline=[str],
      )
  
imports: from tempfile import mkstemp
  from pythran.tests import TestEnv
  import unittest
  from pythran.typing import List
label_desc: Use image node_id 39 for calling the TestFile obj's underlying member method code with example usage: obj.test_rvalue_readline() without return types