Serialization issues with LLMEvaluator and child classes

[anakin87]

I'm encountering issues with serializing LLMEvaluator and child classes (ContextRelevanceEvaluator, FaithfulnessEvaluator).

To Reproduce

from haystack import Pipeline
from haystack.components.evaluators import FaithfulnessEvaluator

pipeline = Pipeline()
pipeline.add_component("ev", FaithfulnessEvaluator())

pipeline.dumps()

Error message

Traceback (most recent call last):
  File "ev.py", line 7, in 
    pipeline.dumps()
  File "/home/anakin87/apps/haystack/haystack/core/pipeline/base.py", line 202, in dumps
    return marshaller.marshal(self.to_dict())
  File "/home/anakin87/apps/haystack/haystack/marshal/yaml.py", line 13, in marshal
    return yaml.dump(dict_)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/__init__.py", line 253, in dump
    return dump_all([data], stream, Dumper=Dumper, **kwds)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/__init__.py", line 241, in dump_all
    dumper.represent(data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 27, in represent
    node = self.represent_data(data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:yaml.org,2002:map', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:yaml.org,2002:map', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:yaml.org,2002:map', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:yaml.org,2002:map', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 199, in represent_list
    return self.represent_sequence('tag:yaml.org,2002:seq', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 92, in represent_sequence
    node_item = self.represent_data(item)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 286, in represent_tuple
    return self.represent_sequence('tag:yaml.org,2002:python/tuple', data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 92, in represent_sequence
    node_item = self.represent_data(item)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 52, in represent_data
    node = self.yaml_multi_representers[data_type](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 346, in represent_object
    return self.represent_sequence(tag+function_name, args)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 92, in represent_sequence
    node_item = self.represent_data(item)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 52, in represent_data
    node = self.yaml_multi_representers[data_type](self, data)
  File "/home/anakin87/apps/haystack/.hatch/haystack-ai/lib/python3.8/site-packages/yaml/representer.py", line 331, in represent_object
    if function.__name__ == '__newobj__':
AttributeError: 'str' object has no attribute '__name__'

Additional context
I encountered several problems, discussed a bit with Massi.

• python types (in inputs: List[Tuple[str, Type[List]]]) are not serialized. -> this causes the error I am encountering. We can take the Multiplexer as an example to serialize types.
• YAML serialization of tuples is problematic (Weaviate: timeout_config is not serialized properly haystack-core-integrations#523 Error when serializing ElasticSearchEmbeddingRetriever from ElasticSearchDocumentStore with authentication haystack-core-integrations#694). If we want to use tuples in the __init__ parameters, we should probably better configure the default marshaller and then check that components can do proper deserialization.
• (I initially thought that the absence of the @component decorator in the child classes was problematic. It probably isn't. It doesn't hurt to check.)

System:

• Haystack version (commit or version number): 2.1.2