/// Helper function to add an [Outline](struct.Outline.html) element with `text` and `xml_url` attributes to the [Body](struct.Body.html). Useful for creating feed lists quickly. This function [also exists on the Outline struct](struct.Outline.html#method.add_feed) to create grouped lists easily.
/// A comma-separated list of line numbers that are expanded. The line numbers in the list tell you which headlines to expand. The order is important. For each element in the list, X, starting at the first summit, navigate flatdown X times and expand. Repeat for each element in the list.
/// A number indicating which line of the outline is displayed on the top line of the window. This number is calculated with the expansion state already applied.
/// Every outline element must have at least a text attribute, which is what is displayed when an outliner opens the OPML document.
/// Version 1.0 OPML documents may omit this attribute, so for compatibility and strictness this attribute is "technically optional" as it will be replaced by an empty String if it is omitted.
/// Text attributes may contain encoded HTML markup.
#[xml(default, attr = "text")]
pubtext: String,
/// A string that indicates how the other attributes of the [Outline](struct.Outline.html) should be interpreted.
#[xml(attr = "type")]
pubr#type: Option<String>,
/// Indicating whether the outline is commented or not. By convention if an outline is commented, all subordinate outlines are considered to also be commented.
#[xml(attr = "isComment")]
pubis_comment: Option<bool>,
/// Indicating whether a breakpoint is set on this outline. This attribute is mainly necessary for outlines used to edit scripts.
#[xml(attr = "isBreakpoint")]
pubis_breakpoint: Option<bool>,
/// The date-time (RFC822) that this [Outline](struct.Outline.html) element was created.
#[xml(attr = "created")]
pubcreated: Option<String>,
/// A string of comma-separated slash-delimited category strings, in the format defined by the [RSS 2.0 category](http://cyber.law.harvard.edu/rss/rss.html#ltcategorygtSubelementOfLtitemgt) element. To represent a "tag," the category string should contain no slashes.
#[xml(attr = "category")]
pubcategory: Option<String>,
/// Child [Outline](struct.Outline.html) elements of the current one.
#[xml(child = "outline")]
puboutlines: Vec<Outline>,
/// The HTTP address of the feed.
#[xml(attr = "xmlUrl")]
pubxml_url: Option<String>,
/// The top-level description element from the feed.
#[xml(attr = "description")]
pubdescription: Option<String>,
/// The top-level link element from the feed.
#[xml(attr = "htmlUrl")]
pubhtml_url: Option<String>,
/// The top-level language element from the feed.
#[xml(attr = "language")]
publanguage: Option<String>,
/// The top-level title element from the feed.
#[xml(attr = "title")]
pubtitle: Option<String>,
/// The version of the feed's format (such as RSS 0.91, 2.0, ...).
#[xml(attr = "version")]
pubversion: Option<String>,
/// A link that can point to another OPML document or to something that can be displayed in a web browser.
/// Helper function to add an [Outline](struct.Outline.html) element with `text` and `xml_url` attributes as a child element. Useful for creating grouped lists. This function [also exists on the OPML struct](struct.OPML.html#method.add_feed) for non-grouped lists.