docstr: Test that the component runs correctly when no files are provided.
code: def test_no_files(self):
      """
      Test that the component runs correctly when no files are provided.
      """
      router = FileTypeRouter(
          mime_types=["text/plain", "audio/x-wav", "image/jpeg"]
      )
      output = router.run(sources=[])
      assert not output
  
file_path: haystack/test/components/routers/test_file_router.py
imports: import sys
  import pytest
  from haystack.components.routers.file_type_router import FileTypeRouter
  from haystack.dataclasses import ByteStream
label_desc: Use image node_id 4 for calling the TestFileTypeRouter obj's underlying member method code with example usage: obj.test_no_files() without return types