def udacity_equation_checker(equation):
    stack = Stack()
    for char in equation:
        if (char == '('):
            stack.push(char)
        elif (char == ')'):
            if (stack.pop() == None):
                return False
    return (stack.size() == 0)
def udacity_equation_checker(equation):
    stack = Stack()
    for char in equation:
        if (char == '('):
            stack.push(char)
        elif (char == ')'):
            if (stack.pop() == None):
                return False
    return (stack.size() == 0)