code: public PBConstraint cc(final CType comparator, final int rhs, final Collection<Variable> variables) {
      final int[] coefficients = new int[variables.size()];
      Arrays.fill(coefficients, 1);
      final Variable[] vars = new Variable[variables.size()];
      int count = 0;
      for (final Variable var : variables)
        vars[count++] = var;
      return this.constructPBC(comparator, rhs, vars, coefficients);
    }
docs: Creates a new cardinality constraint.
  @param variables  the variables of the constraint
  @param comparator the comparator of the constraint
  @param rhs        the right-hand side of the constraint
  @return the cardinality constraint
  @throws IllegalArgumentException if there are negative variables