input: Write a python function to measure the execution time of another function using a decorator.
  @timed_method
  def example_function():
      time.sleep(2)
  assert example_function() is None
output: import time
  from functools import wraps
  
  def timed_method(func):
      @wraps(func)
      def wrapper(*args, **kwargs):
          start_time = time.time()
          result = func(*args, **kwargs)
          end_time = time.time()
          execution_time = end_time - start_time
          print(f"Execution time of {func.__name__}: {execution_time} seconds")
          return result
      return wrapper
  
  @timed_method
  def example_function():
      time.sleep(2)