code: def flat_series(rng):
      index = pd.RangeIndex(10, 30, name="t")
      return pd.Series(rng.normal(size=20), index, name="s")
  
imports: import numpy
  import pandas
  import pytest
label_desc: Use image node_id 6 for calling a global function with example usage: flat_series(rng) and returns: pd