```ruby
# encoding: utf-8

module SQL

  # A mixin for node helpers
  module NodeHelper

    # Return new node
    #
    # @param [Symbol] type
    #
    # @return [AST::Node]
    #
    # @api private
    def s(type, *children)
      AST::Node.new(type, children)
    end

  end # NodeHelper
end # SQL
```

Change the s() method to be private
user
```ruby
# encoding: utf-8

module SQL

  # A mixin for node helpers
  module NodeHelper

    # Return new node
    #
    # @param [Symbol] type
    #
    # @return [AST::Node]
    #
    # @api private
    def s(type, *children)
      AST::Node.new(type, children)
    end
    private :s

  end # NodeHelper
end # SQL
```
assistant