code: def test_project_discover_complicated_suffix(rootdir):
      # complicated source_suffix
      project = Project(rootdir / "test-root", [".foo.png"])
      assert project.discover() == {"img"}
  
file_path: sphinx/tests/test_project.py
imports: import pytest
  from sphinx.project import Project
label_desc: Use image node_id 4 for calling a global function with example usage: test_project_discover_complicated_suffix(rootdir) without return types