public byte[] getBytes(String fieldName) {
        Object bytes = getCheckType(fieldName, Schema.Type.BYTES);
        if (bytes instanceof ByteBuffer)
            return ((ByteBuffer) bytes).array();
        return (byte[]) bytes;
    }
Equivalent to calling {@link #get(String)} and casting the result to a byte[].
connect/api/src/main/java/org/apache/kafka/connect/data/Struct.java