@Override
        public int sizeOf(Object o) {
            if (o == null) {
                return 1;
            }
            int length = Utils.utf8Length((String) o);
            return ByteUtils.sizeOfUnsignedVarint(length + 1) + length;
        }
The Boolean type represents a boolean value in a byte by using
the value of 0 to represent false, and 1 to represent true.

If for some reason a value that is not 0 or 1 is read,
then any non-zero value will return true.
clients/src/main/java/org/apache/kafka/common/protocol/types/Type.java