class_docstr: A uniform accessor that wraps data/schemas of varying formats with a
  common :func:`marshal` function.
code: def format(self):
      return self._format
  
imports: from distutils.util import strtobool
  from math import isnan
  import numpy
  import pandas
  from ..core.data import deconstruct_numpy, deconstruct_pandas, make_null_mask
  from ..core.data.pd import _parse_datetime_index
  from ..core.exception import PerspectiveError
  from ._date_validator import _PerspectiveDateValidator
  from .libpsppy import t_dtype
label_desc: Use image node_id 3 for calling the _PerspectiveAccessor obj's underlying member method code with example usage: obj.format() and returns: self