# File lib/asciidoctor/abstract_node.rb, line 110
  def set_attr(key, val, overwrite = nil)
    if overwrite.nil?
      @attributes[key] = val
      true
    else
      if overwrite || @attributes.has_key?(key)
        @attributes[key] = val
        true
      else
        false
      end
    end
  end