Remove unused internal code

src/black/mode.py

@@ -240,10 +240,6 @@ class Preview(Enum):
 }
 
 
-class Deprecated(UserWarning):
-    """Visible deprecation warning."""
-
-
 _MAX_CACHE_KEY_PART_LENGTH: Final = 32
 
 

src/black/nodes.py

@@ -842,10 +842,6 @@ def is_parent_function_or_class(node: Node) -> bool:
     return node.parent.type in {syms.funcdef, syms.classdef}
 
 
-def is_function_or_class(node: Node) -> bool:
-    return node.type in {syms.funcdef, syms.classdef, syms.async_funcdef}
-
-
 def is_stub_suite(node: Node) -> bool:
     """Return True if `node` is a suite with a stub body."""
     if node.parent is not None and not is_parent_function_or_class(node):

src/black/parsing.py

@@ -102,22 +102,6 @@ def lib2to3_parse(
     return result
 
 
-def matches_grammar(src_txt: str, grammar: Grammar) -> bool:
-    drv = driver.Driver(grammar)
-    try:
-        drv.parse_string(src_txt, False)
-    except (ParseError, TokenError, IndentationError):
-        return False
-    else:
-        return True
-
-
-def lib2to3_unparse(node: Node) -> str:
-    """Given a lib2to3 node, return its string representation."""
-    code = str(node)
-    return code
-
-
 class ASTSafetyError(Exception):
     """Raised when Black's generated code is not equivalent to the old AST."""