code: def test_normalize_metadata_None():
      assert normalize_metadata(None, sources_count=1) == [{}]
      assert normalize_metadata(None, sources_count=3) == [{}, {}, {}]
  
imports: import pytest
  from haystack.components.converters.utils import normalize_metadata
label_desc: Use image node_id 1 for calling a global function with example usage: test_normalize_metadata_None() without return types