The model name to pass to tiktoken when using this class.
Tiktoken is used to count the number of tokens in documents to constrain them to be under a certain limit.
By default, when set to None, this will be the same as the embedding model name.
However, there are some cases where you may want to use this Embedding class with
a model name not supported by tiktoken. This can include when using Azure embeddings
or when using one of the many model providers that expose an OpenAI-like
API but with different models. In those cases, in order to avoid erroring
when tiktoken is called, you can specify a model name to use here.
tiktoken_model_name: str | None = None