Fix mypy typing

src/axolotl/prompters.py

@@ -3,7 +3,7 @@
 import dataclasses
 import logging
 from enum import auto, Enum
-from typing import List, Union, Generator
+from typing import List, Optional, Union, Generator
 
 IGNORE_TOKEN_ID = -100
 
@@ -24,7 +24,7 @@ class AlpacaPrompter:
 
     system_prompt = "Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.\n\n"
     system_no_input_prompt = "Below is an instruction that describes a task. Write a response that appropriately completes the request.\n\n"
-    prompt_style = None
+    prompt_style: Optional[PromptStyle] = None
 
     def __init__(self, prompt_style=PromptStyle.INSTRUCT.value):
         self.prompt_style = prompt_style if prompt_style else PromptStyle.INSTRUCT.value
@@ -231,18 +231,18 @@ class Conversation:
     offset: int
     sep_style: SeparatorStyle = SeparatorStyle.SINGLE
     sep: str = "###"
-    sep2: str = None
+    sep2: Optional[str] = None
 
     def get_prompt(self) -> Generator[str, None, None]:
-        seps = [self.sep, self.sep2]
-        preamble = self.system + seps[0]
+        # seps = [self.sep, self.sep2]
+        preamble = self.system + self.sep
         yield preamble
         for _, (role, message) in enumerate(self.messages):
             if message:
-                yield (role + ":", " " + message)
+                yield role + ":" + " " + message
             else:
                 logging.warning(f"role with empty message: {role}")
-                yield (role + ":",)
+                yield role + ":"
 
     def copy(self):
         return Conversation(