docs: def add_attribute(self, attribute, value):
          """
          Add an attribute to the current instance
  
          :param str attribute: Attribute name
          :type value: Union[datetime,bool,str]
          :param value: Attribute value
          """
          class_name = self.__class__.__name__
          if class_name.startswith('ItemData'):
              # ItemData* Elements
              class_name = 'ItemData'
          if attribute not in MODMExtensionRegistry[class_name].value:
              raise ValueError("Can't add {} to {}".format(attribute, self.__class__.__name__))
          self.attributes.append(MODMAttribute(attribute, value))