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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def validate_packet(self, data):
 """Validate a packet against this packet handler and determine if it meets the requirements. This is done by checking the following conditions are true. - The length of the packet is equal to the first byte. - The second byte is in the set of defined PACKET_TYPES for this class. - The third byte is in the set of this class defined PACKET_SUBTYPES. If one or more of these conditions isn't met then we have a packet that isn't valid or at least isn't understood by this handler. :param data: bytearray to be verified :type data: bytearray :raises: :py:class:`rfxcom.exceptions.InvalidPacketLength`: If the number of bytes in the packet doesn't match the expected length. :raises: :py:class:`rfxcom.exceptions.UnknownPacketType`: If the packet type is unknown to this packet handler :raises: :py:class:`rfxcom.exceptions.UnknownPacketSubtype`: If the packet sub type is unknown to this packet handler :return: true is returned if validation passes. :rtype: boolean """


        # Validate length.
        # The first byte in the packet should be equal to the number of
        # remaining bytes (i.e. length excluding the first byte).
        expected_length = data[0] + 1

        if len(data) != expected_length:
            raise InvalidPacketLength(
                "Expected packet length to be %s bytes but it was %s bytes"
                % (expected_length, len(data))
            )

        # Validate minimal length.
        # The packet contains at least the RFX header:
        #  packet_length (1 byte) + packet_type (1 byte)
        #  + packet_subtype (1 byte) + sequence_number (1 byte)
        if expected_length < 4:
            raise MalformedPacket(
                    "Expected packet length to be larger than 4 bytes but \
                    it was %s bytes"
                    % (len(data))
            )

        # Validate Packet Type.
        # This specifies the family of devices.
        # Check it is one of the supported packet types
        packet_type = data[1]

        if self.PACKET_TYPES and packet_type not in self.PACKET_TYPES:
            types = ",".join("0x{:02x}".format(pt) for pt in self.PACKET_TYPES)
            raise UnknownPacketType(
                "Expected packet type to be one of [%s] but recieved %s"
                % (types, packet_type)
            )

        # Validate Packet Subtype.
        # This specifies the sub-family of devices.
        # Check it is one of the supported packet subtypes for current type
        sub_type = data[2]

        if self.PACKET_SUBTYPES and sub_type not in self.PACKET_SUBTYPES:
            types = \
                ",".join("0x{:02x}".format(pt) for pt in self.PACKET_SUBTYPES)
            raise UnknownPacketSubtype(
                "Expected packet type to be one of [%s] but recieved %s"
                % (types, sub_type))

        return True