old_contents: """
  
  Vulture sometimes reports used code as unused. To avoid these
  false-positives, you can write a Python file that explicitly uses the
  code and pass it to vulture:
  
  vulture myscript.py mydir mywhitelist.py
  
  This file explicitly uses code from the Python standard library that is
  often incorrectly detected as unused.
  
  """
  
  import ast
  import collections
  
  
  # NodeVisitor methods are called implicitly.
  class WhitelistNodeVisitor(ast.NodeVisitor):
      def __getattr__(self, attr):
          pass
  
  whitelist_node_visitor = WhitelistNodeVisitor()
  
  # TODO: Add missing methods.
  whitelist_node_visitor.visit_arg
  whitelist_node_visitor.visit_alias
  whitelist_node_visitor.visit_Assign
  whitelist_node_visitor.visit_Attribute
  whitelist_node_visitor.visit_ClassDef
  whitelist_node_visitor.visit_comprehension
  whitelist_node_visitor.visit_For
  whitelist_node_visitor.visit_FunctionDef
  whitelist_node_visitor.visit_Import
  whitelist_node_visitor.visit_ImportFrom
  whitelist_node_visitor.visit_Name
  whitelist_node_visitor.visit_Str
  
  
  # To free memory, the "default_factory" attribute can be set to None.
  collections.defaultdict(list).default_factory = None
  collections.defaultdict(list).default_factory
  
new_contents: """
  
  Vulture sometimes reports used code as unused. To avoid these
  false-positives, you can write a Python file that explicitly uses the
  code and pass it to vulture:
  
  vulture myscript.py mydir mywhitelist.py
  
  This file explicitly uses code from the Python standard library that is
  often incorrectly detected as unused.
  
  """
  
  import ast
  import collections
  
  
  # NodeVisitor methods are called implicitly.
  class WhitelistNodeVisitor(ast.NodeVisitor):
      def __getattr__(self, attr):
          pass
  
  
  whitelist_node_visitor = WhitelistNodeVisitor()
  
  # TODO: Add missing methods.
  whitelist_node_visitor.visit_arg
  whitelist_node_visitor.visit_alias
  whitelist_node_visitor.visit_Assign
  whitelist_node_visitor.visit_Attribute
  whitelist_node_visitor.visit_ClassDef
  whitelist_node_visitor.visit_comprehension
  whitelist_node_visitor.visit_For
  whitelist_node_visitor.visit_FunctionDef
  whitelist_node_visitor.visit_Import
  whitelist_node_visitor.visit_ImportFrom
  whitelist_node_visitor.visit_Name
  whitelist_node_visitor.visit_Str
  
  
  # To free memory, the "default_factory" attribute can be set to None.
  collections.defaultdict(list).default_factory = None
  collections.defaultdict(list).default_factory
  
subject: fix style