code: def search_file_upwards(name, base=None):
      
      base = base or os.getcwd()
      while base != os.path.dirname(base):
          if os.path.exists(os.path.join(base, name)):
              return base
          base = os.path.dirname(base)
  
      return None
docs: Search for a file named `name` from cwd or given directory to root.
          Return None if nothing's found.