code: def _concat_index_asobject(to_concat, name=None):
      
      from pandas import Index
      from pandas.core.arrays import ExtensionArray
  
      klasses = (ABCDatetimeIndex, ABCTimedeltaIndex, ABCPeriodIndex,
                 ExtensionArray)
      to_concat = [x.astype(object) if isinstance(x, klasses) else x
                   for x in to_concat]
  
      self = to_concat[0]
      attribs = self._get_attributes_dict()
      attribs['name'] = name
  
      to_concat = [x._values if isinstance(x, Index) else x
                   for x in to_concat]
  
      return self._shallow_copy_with_infer(np.concatenate(to_concat), **attribs)
docs: concat all inputs as object. DatetimeIndex, TimedeltaIndex and
      PeriodIndex are converted to object dtype before concatenation