class_docstr: Storage type of a mapped operator's mapped kwargs.
  
  This is created from ``expand(**kwargs)``.
code: def _expand_mapped_field(
      self, key: str, value: Any, context: Context, *, session: Session
  ) -> Any:
      if _needs_run_time_resolution(value):
          value = value.resolve(context, session=session)
      map_index = context["ti"].map_index
      if map_index < 0:
          raise RuntimeError(
              "can't resolve task-mapping argument without expanding"
          )
      all_lengths = self._get_map_lengths(
          context["run_id"], session=session
      )
  
      def _find_index_for_this_field(index: int) -> int:
          # Need to use the original user input to retain argument order.
          for mapped_key in reversed(self.value):
              mapped_length = all_lengths[mapped_key]
              if mapped_length < 1:
                  raise RuntimeError(
                      f"cannot expand field mapped to length {mapped_length!r}"
                  )
              if mapped_key == key:
                  return index % mapped_length
              index //= mapped_length
          return -1
  
      found_index = _find_index_for_this_field(map_index)
      if found_index < 0:
          return value
      if isinstance(value, collections.abc.Sequence):
          return value[found_index]
      if not isinstance(value, dict):
          raise TypeError(f"can't map over value of type {type(value)}")
      for i, (k, v) in enumerate(value.items()):
          if i == found_index:
              return k, v
      raise IndexError(f"index {map_index} is over mapped length")
  
imports: from __future__ import annotations
  import collections.abc
  import functools
  import operator
  from typing import TYPE_CHECKING, Any, Dict, Iterable, Mapping, NamedTuple, Sequence, Sized, Union
  import attr
  from airflow.utils.mixins import ResolveMixin
  from airflow.utils.session import NEW_SESSION, provide_session
label_desc: Use image node_id 5 for calling the DictOfListsExpandInput obj's underlying member method code with example usage: obj._expand_mapped_field(key, value, context) and returns: unknown, value, value, k,  v, unknown