code: def test_docstring_inheritor():
      class A(metaclass=DocStringInheritor):
          """
          Docstring
          """
  
      class B(A):
          pass
  
      assert_equal(B.__doc__, A.__doc__)
  
imports: from abc import abstractmethod
  import datetime
  import numpy
  from numpy.random import RandomState
  from numpy.testing import assert_equal
  from pandas import DataFrame, Series, Timedelta, date_range
  import pytest
  from arch import doc
  from arch.univariate.base import implicit_constant
  from arch.utility.array import ConcreteClassMeta, DocStringInheritor, cutoff_to_index, date_to_index, ensure1d, ensure2d, find_index, parse_dataframe
label_desc: Use image node_id 6 for calling a global function with example usage: test_docstring_inheritor() without return types