code: def resources(self):
          
          with open(os.path.join(EULER_DATA, 'resources.json')) as data_file:
              data = json.load(data_file)
  
          problem_num = str(self.num)
  
          if problem_num in data:
              files = data[problem_num]
  
              # Ensure a list of files is returned
              return files if isinstance(files, list) else [files]
          else:
              return None
docs: Returns a list of resources related to the problem (or None)