Same token usage. Actually OpenAI returns the logprob of each token conditional on the previous ones with the option logprobs=true. This lib simply parses the o

Same token usage. Actually OpenAI returns the logprob of each token conditional on the previous ones with the option logprobs=true. This lib simply parses the output json string with `lark` into an AST with value nodes. The value nodes are mapped back to a range of characters in the json string. Then the characters are mapped back to the GPT tokens overlapping the character ranges and the logprobs of the tokens are summed.