code: def property(self, property_name, default=Ellipsis):
          
          try:
              return self._a_tags[property_name]
          except KeyError:
              if default != Ellipsis:
                  return default
              else:
                  raise
docs: Returns a property value
  
          :param: default will return that value if the property is not found,
                 else, will raise a KeyError.