code: def test_process_start_field(freq, expected, given):
      assert pd.Period(given, freq) == pd.Period(expected, freq)
  
imports: import pandas
  import pytest
  from gluonts.dataset.common import Dataset
label_desc: Use image node_id 1 for calling a global function with example usage: test_process_start_field(freq, expected, given) without return types