This contains the Packet Identifier.
The list of Topic Filters that the Client wishes to unsubscribe from. The Topic Filters in an UNSUBSCRIBE packet MUST be UTF-8 encoded strings. The Payload of an UNSUBSCRIBE packet MUST contain at least one Topic Filter. An UNSUBSCRIBE packet with no payload is a protocol violation.
An UNSUBSCRIBE Packet is sent by the Client to the Server, to unsubscribe from topics.