code: def test_show_source_returns_nothing():
      """Verify Nothing.show_source returns None."""
      formatter = default.Nothing(options())
      error = Violation("code", "file.py", 1, 1, "text", "1")
  
      assert formatter.show_source(error) is None
  
imports: from __future__ import annotations
  import argparse
  from flake8.formatting import default
  from flake8.violation import Violation
label_desc: Use image node_id 3 for calling a global function with example usage: test_show_source_returns_nothing() without return types