class_docstr: Manage and provide access to all of the models that belong to a Bokeh
  Document.
  
  The set of "all models" means specifically all the models reachable from
  references form a Document's roots.
class_docstr_tok: ["Manage","and","provide","access","to","all","of","the","models","that","belong","to","a","Bokeh","Document",".","The","set","of","``","all","models","''","means","specifically","all","the","models","reachable","from","references","form","a","Document","'s","roots","."]
docstr: Report whether a model id has ever previously belonged to this
  Document.
  
  Args:
      id (ID) : the model id of a model to check
  
  Returns:
      bool
docstr_tok: ["Report","whether","a","model","id","has","ever","previously","belonged","to","this","Document",".","Args",":","id","(","ID",")",":","the","model","id","of","a","model","to","check","Returns",":","bool"]
code: def seen(self, id: ID) -> bool:
      """Report whether a model id has ever previously belonged to this
      Document.
  
      Args:
          id (ID) : the model id of a model to check
  
      Returns:
          bool
  
      """
      return id in self._seen_model_ids
  
imports: from __future__ import annotations
  import logging
  import contextlib
  import weakref
  from typing import TYPE_CHECKING, Callable, Generator, Iterator
  from ..core.types import ID
  from ..model import Model
  from ..util.datatypes import MultiValuedDict
label_desc: Use image node_id 16 for calling the DocumentModelManager obj's underlying member method code with example usage: obj.seen(id) and returns: unknown