def add_warning(message, filename = @node.file, line_number = @node.line_number)
      warnings << Warning.new(filename: filename, line_number: line_number, message: message)
    end
def add_warning(message, filename = @node.file, line_number = @node.line_number)
      warnings << Warning.new(filename: filename, line_number: line_number, message: message)
    end
add an warning.

 @param [String] message, is the warning message
 @param [String] filename, is the filename of source code
 @param [Integer] line_number, is the line number of the source code which is reviewing