Remove cookie attribute. Cookie attribute couldn't be removed if cookie is in read-only mode
		(RuntimeError exception is raised).

		:param attr_name: name of attribute to remove
		:return: None

def remove_attr(self, attr_name):
		""" Remove cookie attribute. Cookie attribute couldn't be removed if cookie is in read-only mode
		(RuntimeError exception is raised).

		:param attr_name: name of attribute to remove
		:return: None
		"""
		if self.__ro_flag:
			raise RuntimeError('Read-only cookie changing attempt')
		name = self.__attr_name(attr_name)
		if name in self.__attrs.keys():
			self.__attrs.pop(attr_name)