code: def gen_begin(self, in_tokens, mask=None):
      self.end_beam_search()
  
      self.sequence = in_tokens.clone()
      self.sequence_actual = in_tokens.clone()
      self.cache.current_seq_len = 0
  
      self.model.forward(
          self.sequence[:, :-1],
          self.cache,
          preprocess_only=True,
          lora=self.lora,
          input_mask=mask,
      )
  
imports: import cuda_ext
  from model import ExLlama, ExLlamaCache
  from lora import ExLlamaLora
  import torch
  import torch.nn.functional
label_desc: Use image node_id 8 for calling the ExLlamaGenerator obj's underlying member method code with example usage: obj.gen_begin(in_tokens, mask) without return types