def check(filename, content)
      node = parse(filename, content)
      node.file = filename
      check_node(node)
    end
def check(filename, content)
      node = parse(filename, content)
      node.file = filename
      check_node(node)
    end
check the ruby sexp nodes for the ruby file.

 @param [String] filename is the filename of ruby code.
 @param [String] content is the content of ruby file.