public ScriptBuilder data(byte[] data){
  if (data.length == 0)   return smallNum(0);
 else   return data(chunks.size(),data);
}

public ScriptBuilder data ( byte [ ] data ) { if ( data . length == 0 ) return smallNum ( 0 ) ; else return data ( chunks . size ( ) , data ) ; }
adds a copy of the given byte array as a data element ( i . e . pushdata ) at the end of the program .
