code: def forward(self, prefix: torch.Tensor):
      if self.prefix_projection:
          prefix_tokens = self.embedding(prefix)
          past_key_values = self.transform(prefix_tokens)
      else:
          past_key_values = self.embedding(prefix)
      return past_key_values
  
imports: import torch
label_desc: Use image node_id 2 for calling the PrefixEncoder obj's underlying member method code with example usage: obj.forward(prefix) and returns: past_key_values