[BUG]: After building the listener through graph, an error occurs when executing db.add.

[jieguangzhou]

Contact Details [Optional]

No response

System Information

main branch

What happened?

If Variable is a key, setting is skipped

Steps to reproduce

from superduperdb import superduper
from superduperdb.backends.mongodb import Collection

db = superduper('mongomock://temp')
select = Collection("data").find()

from superduperdb import ObjectModel
model1 = ObjectModel(identifier="model1", object=lambda x: "model1_" + str(x))
model2 = ObjectModel(identifier="model2", object=lambda x1, x2: {"x1": x1, "x2":x2})

from superduperdb.components.graph import Graph, document_node, input_node
in_ = document_node('x')
output1 = model1(x=in_['x'], outputs="l1")
output2 = model2(x1=output1, x2=in_["x"], outputs="l2")
listener_stack = output2.to_listeners(select=select, identifier="listener")
db.add(listener_stack)

Relevant log output

File ~/workspace/SuperDuperDB/superduperdb/superduperdb/base/datalayer.py:484, in Datalayer.add(self, object, dependencies)
    476     return type(object)(
    477         self._add(
    478             object=component,
   (...)
    481         for component in object
    482     )
    483 elif isinstance(object, Component):
--> 484     return self._add(object=object, dependencies=dependencies), object
    485 else:
    486     return self._add(superduper(object)), object

File ~/workspace/SuperDuperDB/superduperdb/superduperdb/base/datalayer.py:852, in Datalayer._add(self, object, dependencies, parent)
    850 artifacts = [leaf for leaf in leaves if isinstance(leaf, _BaseEncodable)]
    851 children = [leaf for leaf in leaves if isinstance(leaf, Component)]
--> 852 jobs.extend(self._add_child_components(children, parent=object))
    854 # need to do this again to get the versions of the children
    855 object.set_variables(self)

File ~/workspace/SuperDuperDB/superduperdb/superduperdb/base/datalayer.py:812, in Datalayer._add_child_components(self, components, parent)
    808     component = lookup[n]
    809     dependencies = sum(
    810         [jobs.get(d[:2], []) for d in component.dependencies], []
    811     )
--> 812     tmp = self._add(
    813         component, parent=parent.unique_id, dependencies=dependencies
    814     )
    815     jobs[n] = tmp
    817 return sum(list(jobs.values()), [])

File ~/workspace/SuperDuperDB/superduperdb/superduperdb/base/datalayer.py:861, in Datalayer._add(self, object, dependencies, parent)
    858 if artifacts:
    859     self.artifact_store.save(serialized)
--> 861 self.metadata.create_component(serialized)
    863 if parent is not None:
    864     self.metadata.create_parent_child(parent, object.unique_id)

File ~/workspace/SuperDuperDB/superduperdb/superduperdb/backends/mongodb/metadata.py:63, in MongoMetaDataStore.create_component(self, info)
     61 if 'hidden' not in info:
     62     info['hidden'] = False
---> 63 return self.component_collection.insert_one(info)

File ~/workspace/SuperDuperDB/superduperdb/env/lib/python3.10/site-packages/mongomock/collection.py:454, in Collection.insert_one(self, document, bypass_document_validation, session)
    452 if not bypass_document_validation:
    453     validate_is_mutable_mapping('document', document)
--> 454 return InsertOneResult(self._insert(document, session), acknowledged=True)

File ~/workspace/SuperDuperDB/superduperdb/env/lib/python3.10/site-packages/mongomock/collection.py:505, in Collection._insert(self, data, session, ordered)
    501     raise ValueError('Document keys must be strings')
    503 if BSON:
    504     # bson validation
--> 505     BSON.encode(data, check_keys=True)
    507 # Like pymongo, we should fill the _id in the inserted dict (odd behavior,
    508 # but we need to stick to it), so we must patch in-place the data dict
    509 if '_id' not in data:

File ~/workspace/SuperDuperDB/superduperdb/env/lib/python3.10/site-packages/bson/__init__.py:1428, in BSON.encode(cls, document, check_keys, codec_options)
   1401 @classmethod
   1402 def encode(
   1403     cls: Type[BSON],
   (...)
   1406     codec_options: CodecOptions[Any] = DEFAULT_CODEC_OPTIONS,
   1407 ) -> BSON:
   1408     """Encode a document to a new :class:`BSON` instance.
   1409
   1410     A document can be any mapping type (like :class:`dict`).
   (...)
   1426        Replaced `uuid_subtype` option with `codec_options`.
   1427     """
-> 1428     return cls(encode(document, check_keys, codec_options))

File ~/workspace/SuperDuperDB/superduperdb/env/lib/python3.10/site-packages/bson/__init__.py:1042, in encode(document, check_keys, codec_options)
   1039 if not isinstance(codec_options, CodecOptions):
   1040     raise _CODEC_OPTIONS_TYPE_ERROR
-> 1042 return _dict_to_bson(document, check_keys, codec_options)

InvalidDocument: documents must have only string keys, key was $_outputs.l1::{version}