further cleanups

DHParser/parser.py

@@ -956,7 +956,7 @@ def dsl_error_msg(parser: Parser, error_str: str) -> str:
 ########################################################################
 
 
-RX_PREPROCESSOR_TOKEN = re.compile('\w+')
+RX_PREPROCESSOR_TOKEN = re.compile(r'\w+')
 BEGIN_TOKEN = '\x1b'
 END_TOKEN = '\x1c'
 
@@ -977,6 +977,7 @@ def make_token(token: str, argument: str = '') -> str:
 
 
 def nil_preprocessor(text: str) -> str:
+    """A preprocessor that does nothing, i.e. just returns the input."""
     return text
 
 
@@ -1065,6 +1066,7 @@ class RegExp(Parser):
 
 
 class Whitespace(RegExp):
+    """A parser class for plain whitespace."""
     assert WHITESPACE_PTYPE == ":Whitespace"
 
 

DHParser/syntaxtree.py

@@ -88,15 +88,15 @@ class ParserBase:
         """Resets any parser variables. (Should be overridden.)"""
         pass
 
-    def grammar(self) -> Optional['Grammar']:
+    def grammar(self) -> Optional[object]:
         """Returns the Grammar object to which the parser belongs. If not
         yet connected to any Grammar object, None is returned."""
         return None
 
     def apply(self, func: Callable) -> bool:
-        """Applies the function `func` to the parser. Returns False, if 
+        """Applies the function `func` to the parser. Returns False, if
         - for whatever reason - the functions has not been applied, True
-        otherwise.""" 
+        otherwise."""
         return False