code: def create_rules(aes, value):
      
      if isinstance(value, six.string_types):
          return Rules(aes)
      else:
          rules = Rules()
          for idx, (pattern, css_value) in enumerate(value):
              rules.add_rule(pattern, '{0}_{1}'.format(aes, idx))
          return rules
docs: Create a Rules instance for a single aesthetic value.
  
      Parameter
      ---------
      aes: str
          The name of the aesthetic
      value: str or list
          The value associated with any aesthetic