code: public boolean removeTerms(Set<BooleanTerm> toRemove) {
  		boolean modified = false;
  		if (toRemove == null || toRemove.iterator() == null) {
  			modified = booleanTerms == null || size() != 0;
  			booleanTerms = new HashSet<BooleanTerm>();
  		} else if (booleanTerms != null) {
  			modified = removeAll(toRemove);
  		}
  		return modified;
  	}
docs: Removes the specified terms from the formula
  
  @param toRemove The set of terms to remove
  @return True if the formula was modified