add chat template for Yi (#779)

lmdeploy/model.py

@@ -716,6 +716,79 @@ class UltraChat(BaseModel):
         return ret
 
 
+@MODELS.register_module(name='yi')
+class Yi(BaseModel):
+    """Chat template of Yi model."""
+
+    def __init__(self,
+                 system='<|im_start|>system\n',
+                 meta_instruction=None,
+                 user='<|im_start|>user\n',
+                 eoh='<|im_end|>\n',
+                 eoa='<|im_end|>\n',
+                 eosys='<|im_end|>\n',
+                 assistant='<|im_start|>assistant\n',
+                 stop_words=['<|im_end|>', '<|endoftext|>'],
+                 **kwargs):
+        super().__init__(**kwargs)
+        self.system = system
+        self.meta_instruction = meta_instruction
+        self.user = user
+        self.eoh = eoh
+        self.eoa = eoa
+        self.eosys = eosys
+        self.assistant = assistant
+        self.stop_words = stop_words
+
+    def decorate_prompt(self, prompt, sequence_start=True):
+        """Return the prompt that is concatenated with other elements in the
+        chat template.
+
+        Args:
+            prompt (str): user's input prompt
+            sequence_start (bool): indicator for the first round chat of a
+               session sequence
+        Returns:
+            str: the concatenated prompt
+        """
+        assert self.capability == 'chat', \
+            f'{type(self).__name__} has no capability of {self.capability}'
+        if sequence_start:
+            if self.meta_instruction is None:
+                return f'{self.user}{prompt}{self.eoh}' \
+                   f'{self.assistant}'
+            return f'{self.system}{self.meta_instruction}{self.eosys}' \
+                   f'{self.user}{prompt}{self.eoh}' \
+                   f'{self.assistant}'
+        else:
+            return f'{self.user}{prompt}{self.eoh}' \
+                   f'{self.assistant}'
+
+    def messages2prompt(self, messages, sequence_start=True):
+        """Return the prompt that is concatenated with other elements in the
+        chat template.
+
+        Args:
+            messages (str | List): user's input prompt
+        Returns:
+            str: the concatenated prompt
+        """
+
+        if isinstance(messages, str):
+            return self.get_prompt(messages, sequence_start)
+        eox_map = dict(user=self.eoh, assistant=self.eoa, system=self.eosys)
+        ret = ''
+        if self.meta_instruction:
+            ret += f'{self.system}:{self.meta_instruction}{self.eosys}'
+
+        for message in messages:
+            role = message['role']
+            content = message['content']
+            ret += f'{eval(f"self.{role}")}{content}{eox_map[role]}'
+        ret += f'{self.assistant}'
+        return ret
+
+
 def main(model_name: str = 'test'):
     assert model_name in MODELS.module_dict.keys(), \
         f"'{model_name}' is not supported. " \