Better gemini model names support

[megatron6000]

Feature Description

Currently model names like gemini-1.5-pro-preview-0514 raise errors. It's because the library that is used to calculate the tokens offline lack support for names like that. To fix that, only the "core" of the name can be used to init the tokenizer (i.e. gemini-1.5-pro ).

Changed

• if initializing tokenizer with a model name provided in config doesn't work, initialization only with the "core" of the model name is tried, and only if this won't work the error is raised.