Is this class serializable?
Base class for content used in retrieval and data processing workflows.
Provides common fields for content that needs to be stored, indexed, or searched.
For multimodal content in chat messages (images, audio sent to/from LLMs),
use langchain.messages content blocks instead.
An optional identifier for the document.
Ideally this should be unique across the document collection and formatted as a UUID, but this will not be enforced.
Arbitrary metadata associated with the content.
