class_docstr: Data handling class which knows how to reattach pandas metadata to model
  results
class_docstr_tok: ["Data","handling","class","which","knows","how","to","reattach","pandas","metadata","to","model","results"]
code: def _drop_nans_2d(cls, x, nan_mask):
      if isinstance(x, (Series, DataFrame)):
          return x.loc[nan_mask].loc[:, nan_mask]
      else:  # extra arguments could be plain ndarrays
          return super()._drop_nans_2d(x, nan_mask)
  
imports: from __future__ import annotations
  from statsmodels.compat.python import lmap
  from functools import reduce
  import numpy
  from pandas import DataFrame, Series, isnull, MultiIndex
  import statsmodels.tools.data
  from statsmodels.tools.decorators import cache_readonly, cache_writable
  from statsmodels.tools.sm_exceptions import MissingDataError
label_desc: Use image node_id 3 for calling the PandasData obj's underlying member method code with example usage: obj._drop_nans_2d(cls, x, nan_mask) and returns: x, super