Classes to both filter and generically type-cast nodes of a document based on type, name, value, or other aspects, and to boolean AND/OR/NEGATE these rules. Filters can be used in methods like getContent(Filter) and getDescendants(Filter). Filters are also used extensively in the XPath API. The `Filters` class provides access to a large number of useful filters, and also a sampling of generally useful filters is provided here. Additional filters can be user defined, and that is made easier by extending thr AbstractFilter class.