code: def test_convert_nested(self, pc, axis):
      data = ["2012-1-1", "2012-1-2"]
      r1 = pc.convert([data, data], None, axis)
      r2 = [pc.convert(data, None, axis) for _ in range(2)]
      assert r1 == r2
  
imports: from datetime import date, datetime
  import subprocess
  import sys
  import numpy
  import pytest
  import pandas._config.config
  from pandas._libs.tslibs import to_offset
  from pandas import Index, Period, PeriodIndex, Series, Timestamp, arrays, date_range
  import pandas._testing
  from pandas.plotting import deregister_matplotlib_converters, register_matplotlib_converters
  from pandas.tseries.offsets import Day, Micro, Milli, Second
label_desc: Use image node_id 6 for calling the TestPeriodConverter obj's underlying member method code with example usage: obj.test_convert_nested(pc, axis) without return types