old_contents: 
  class Patch(object):
      """
      Implements a class decorator suitable for patching an existing class with
      a new namespace.
  
      For example, consider this trivial class (that your code doesn't own):
  
      >>> class MyClass:
      ...     def __init__(self, param):
      ...         self.param = param
      ...     def bar(self):
      ...         print("orig bar")
  
      To add attributes to MyClass, you can use MonkeyPatch:
  
      >>> @Patch(MyClass)
      ... class JustANamespace:
      ...     def print_param(self):
      ...         print(self.param)
      >>> ob = MyClass('foo')
      >>> ob.print_param()
      foo
  
      The namespace is assigned None, so there's no mistaking the purpose
      >>> JustANamespace
  
      The patcher will replace the existing methods:
  
      >>> @Patch(MyClass)
      ... class SomeNamespace:
      ...     def bar(self):
      ...         print("replaced bar")
      >>> ob = MyClass('foo')
      >>> ob.bar()
      replaced bar
  
      But it will not replace methods if no_replace is indicated.
  
      >>> @Patch(MyClass)
      ... class AnotherNamespace:
      ...     @no_replace
      ...     def bar(self):
      ...         print("candy bar")
      >>> ob = MyClass('foo')
      >>> ob.bar()
      replaced bar
  
      """
  
      def __init__(self, target):
          self.target = target
  
      def __call__(self, patches):
          for name, value in vars(patches).items():
              if name in vars(ReferenceEmptyClass):
                  continue
              no_replace = getattr(value, '__no_replace', False)
              if no_replace and hasattr(self.target, name):
                  continue
              setattr(self.target, name, value)
  
  def no_replace(f):
      """
      Method decorator to indicate that a method definition shall
      silently be ignored if it already exists in the target class.
      """
      f.__no_replace = True
      return f
  
  class ReferenceEmptyClass(object):
      """
      This empty class will serve as a reference for attributes present on
      any class.
      """
  
new_contents: 
  class Patch(object):
      """
      Implements a class decorator suitable for patching an existing class with
      a new namespace.
  
      For example, consider this trivial class (that your code doesn't own):
  
      >>> class MyClass:
      ...     def __init__(self, param):
      ...         self.param = param
      ...     def bar(self):
      ...         print("orig bar")
  
      To add attributes to MyClass, you can use Patch:
  
      >>> @Patch(MyClass)
      ... class JustANamespace:
      ...     def print_param(self):
      ...         print(self.param)
      >>> ob = MyClass('foo')
      >>> ob.print_param()
      foo
  
      The namespace is assigned None, so there's no mistaking the purpose
      >>> JustANamespace
  
      The patcher will replace the existing methods:
  
      >>> @Patch(MyClass)
      ... class SomeNamespace:
      ...     def bar(self):
      ...         print("replaced bar")
      >>> ob = MyClass('foo')
      >>> ob.bar()
      replaced bar
  
      But it will not replace methods if no_replace is indicated.
  
      >>> @Patch(MyClass)
      ... class AnotherNamespace:
      ...     @no_replace
      ...     def bar(self):
      ...         print("candy bar")
      >>> ob = MyClass('foo')
      >>> ob.bar()
      replaced bar
  
      """
  
      def __init__(self, target):
          self.target = target
  
      def __call__(self, patches):
          for name, value in vars(patches).items():
              if name in vars(ReferenceEmptyClass):
                  continue
              no_replace = getattr(value, '__no_replace', False)
              if no_replace and hasattr(self.target, name):
                  continue
              setattr(self.target, name, value)
  
  def no_replace(f):
      """
      Method decorator to indicate that a method definition shall
      silently be ignored if it already exists in the target class.
      """
      f.__no_replace = True
      return f
  
  class ReferenceEmptyClass(object):
      """
      This empty class will serve as a reference for attributes present on
      any class.
      """
  
subject: Correct docstring