Refactor Request: Grammar should be put as string in the example scripts to help run directly

[Saibo-creator]

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
from transformers_cfg.grammar_utils import IncrementalGrammarConstraint
from transformers_cfg.generation.logits_process import GrammarConstrainedLogitsProcessor


if __name__ == "__main__":

    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    print(f"Using device: {device}")

    model_id = "mistralai/Mistral-7B-v0.1"

    # Load model and tokenizer
    tokenizer = AutoTokenizer.from_pretrained(model_id)
    tokenizer.pad_token = tokenizer.eos_token

    model = AutoModelForCausalLM.from_pretrained(model_id).to(
        device
    )  # Load model to defined device
    model.generation_config.pad_token_id = model.generation_config.eos_token_id

    model = AutoModelForCausalLM.from_pretrained(model_id).to(
        device
    )  # Load model to defined device
    model.generation_config.pad_token_id = model.generation_config.eos_token_id

    grammar_str = """
    # Grammar for subset of JSON
    # String doesn't support unicode and escape yet
    # If you don't need to generate unicode and escape, you can use this grammar
    # We are working to support unicode and escape

    root   ::= object

    object ::= "{" ws ( string ":" ws value ("," ws string ":" ws value)* )? "}"

    value  ::= object | array | string | number | ("true" | "false" | "null") ws

    array  ::= "[" ws ( value ("," ws value)* )? "]" ws

    string ::= "\"" [ \t!#-\[\]-~]* "\"" ws

    number ::= ("-"? ([0-9] | [1-9] [0-9]*)) ("." [0-9]+)? ([eE] [-+]? [0-9]+)? ws


    ws ::= ([ \t\n] ws)?
    """
    grammar = IncrementalGrammarConstraint(grammar_str, "root", tokenizer)
    grammar_processor = GrammarConstrainedLogitsProcessor(grammar)

    # Generate
    prefix1 = "This is a valid json string for http request:"
    prefix2 = "This is a valid json string for shopping cart:"
    input_ids = tokenizer(
        [prefix1, prefix2], add_special_tokens=False, return_tensors="pt", padding=True
    )["input_ids"].to(
        device
    )  # Move input_ids to the same device as model

    output = model.generate(
        input_ids,
        do_sample=False,
        max_new_tokens=60,
        logits_processor=[grammar_processor],
        repetition_penalty=1.1,
        num_return_sequences=1,
    )
    # decode output
    generations = tokenizer.batch_decode(output, skip_special_tokens=True)
    print(generations)

    """
    'This is a valid json string for http request:{ "request": { "method": "GET", "headers": [], "content": "Content","type": "application" }}
    'This is a valid json string for shopping cart:This is a valid json string for shopping cart:{ "name": "MyCart", "price": 0, "value": 1 }
    """