question: public ByteStringBuilder appendBytes ( final byte [ ] bytes , final int offset , final int length ) { ByteString . checkArrayBounds ( bytes , offset , length ) ; if ( length != 0 ) { ensureAdditionalCapacity ( length ) ; System . arraycopy ( bytes , offset , buffer , this . length , length ) ; this . length += length ; } return this ; }
target:  Appends the provided byte array to this byte string builder.