instance method to_tag

# File activesupport/lib/active_support/xml_mini.rb, line 115
    def to_tag(key, value, options)
      type_name = options.delete(:type)
      merged_options = options.merge(root: key, skip_instruct: true)

      if value.is_a?(::Method) || value.is_a?(::Proc)
        if value.arity == 1
          value.call(merged_options)
        else
          value.call(merged_options, key.to_s.singularize)
        end
      elsif value.respond_to?(:to_xml)
        value.to_xml(merged_options)
      else
        type_name ||= TYPE_NAMES[value.class.name]
        type_name ||= value.class.name if value && !value.respond_to?(:to_str)
        type_name   = type_name.to_s   if type_name
        type_name   = "dateTime" if type_name == "datetime"

        key = rename_key(key.to_s, options)

        attributes = options[:skip_types] || type_name.nil? ? {} : { type: type_name }
        attributes[:nil] = true if value.nil?

        encoding = options[:encoding] || DEFAULT_ENCODINGS[type_name]
        attributes[:encoding] = encoding if encoding

        formatted_value = FORMATTING[type_name] && !value.nil? ?
          FORMATTING[type_name].call(value) : value

        options[:builder].tag!(key, formatted_value, attributes)
      end
    end