code: public static IsLessThanOrEqual isLessThanOrEqual(NumberExpression left, Object constant) {
  
          if (!(constant instanceof Number))
              throw new IllegalArgumentException("constant is not a Number");
  
          return new IsLessThanOrEqual(left, constant((Number)constant));
      }
docs: Creates an IsLessThanOrEqual expression from the given expression and constant.
  
  @param left  The left expression.
  @param constant The constant to compare to (must be a Number).
  @throws IllegalArgumentException If the constant is not a Number
  @return A new is less than binary expression.