code: public final static boolean doesSequenceContainInvalidChar(String sequence, Set<Character> cSet){
  		for(char c:sequence.toCharArray()){
  			if(!cSet.contains(c)) return true;
  		}
  		return false;
  	}
docs: Checks if given sequence contains invalid characters. Returns true if invalid characters are found, else return false.
  Note that any characters are deemed as valid only if it is found in cSet.
  
  @param sequence
  protein sequence to be check.
  @param cSet
  the set of characters that are deemed valid.
  @return
  true if invalid characters are found, else return false.