code: def test_to_df_from_df():
      df = pd.DataFrame({"a": [1, 2, 3]})
      out = nbcollection.to_df(df)
  
      assert df.equals(out)
      assert df.columns == out.columns
      assert df.index.name == out.index.name
  
imports: import pytest
  import pandas
  import numpy
  from sklearn_evaluation import NotebookCollection
  from sklearn_evaluation.nb import NotebookCollection
  from IPython.display import HTML
label_desc: Use image node_id 8 for calling a global function with example usage: test_to_df_from_df() without return types