class_docstr: Raise when ``get_map_lengths`` cannot populate all mapping metadata.
  
  This is generally due to not all upstream tasks have finished when the
  function is called.
code: def __init__(self, missing: set[str]) -> None:
      self.missing = missing
  
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 1 to create a new NotFullyPopulated object from inherited base classes: RuntimeError with example: obj = NotFullyPopulated(missing)