Replace '...' with 'NotImplemented'

lark/indenter.py

@@ -74,31 +74,31 @@ class Indenter(PostLex, ABC):
     @property
     @abstractmethod
     def NL_type(self) -> str:
-        ...
+        return NotImplemented
 
     @property
     @abstractmethod
     def OPEN_PAREN_types(self) -> List[str]:
-        ...
+        return NotImplemented
 
     @property
     @abstractmethod
     def CLOSE_PAREN_types(self) -> List[str]:
-        ...
+        return NotImplemented
 
     @property
     @abstractmethod
     def INDENT_type(self) -> str:
-        ...
+        return NotImplemented
 
     @property
     @abstractmethod
     def DEDENT_type(self) -> str:
-        ...
+        return NotImplemented
 
     @property
     @abstractmethod
     def tab_len(self) -> int:
-        ...
+        return NotImplemented
 
 ###}

lark/lexer.py

@@ -359,7 +359,7 @@ class Lexer(ABC):
     """
     @abstractmethod
     def lex(self, lexer_state: LexerState, parser_state: Any) -> Iterator[Token]:
-        ...
+        return NotImplemented
 
     def make_lexer_state(self, text):
         line_ctr = LineCounter(b'\n' if isinstance(text, bytes) else '\n')