code: def deprecated(msg=None, stacklevel=2):
      
      def deprecated_dec(fn):
          @wraps(fn)
          def wrapper(*args, **kwargs):
              warnings.warn(
                  msg or "Function %s is deprecated." % fn.__name__,
                  category=DeprecationWarning,
                  stacklevel=stacklevel
              )
              return fn(*args, **kwargs)
          return wrapper
      return deprecated_dec
docs: Used to mark a function as deprecated.
  
      Parameters
      ----------
      msg : str
          The message to display in the deprecation warning.
      stacklevel : int
          How far up the stack the warning needs to go, before
          showing the relevant calling lines.
  
      Examples
      --------
      @deprecated(msg='function_a is deprecated! Use function_b instead.')
      def function_a(*args, **kwargs):