code: def periods(self):
      return self._periods
  
imports: import itertools
  import numpy
  from ...None import opcodes
  from ...core import recursive_tile
  from ...serialization.serializables import AnyField, Int8Field, Int64Field
  from ..core import DATAFRAME_TYPE, OutputType
  from ..operands import DataFrameOperand, DataFrameOperandMixin
  from ..utils import build_empty_df, build_empty_series, validate_axis
  from .shift import DataFrameShift
label_desc: Use image node_id 1 for calling the DataFrameDiff obj's underlying member method code with example usage: obj.periods() and returns: self