code: public String convert(ProteinSequence sequence){
  		String convertedSequence = "";
  		String uppercaseSequence = sequence.getSequenceAsString().toUpperCase();
  		for(int x = 0; x < uppercaseSequence.length(); x++){
  			convertedSequence += String.valueOf(convert(uppercaseSequence.charAt(x)));
  		}
  		return convertedSequence;
  	}
docs: Returns the converted sequence.
  The sequence argument must be a protein sequence consisting of preferably non-ambiguous characters only.
  Standard amino acids will be converted to '1', '2' or '3' depending on its grouping
  Non-standard amino acids are simply converted to '0'.
  
  @param sequence
  a protein sequence consisting of preferably non-ambiguous characters only
  @return the converted sequence