def dependencies
      _dependencies(Set.new, engines = Set.new)
      Sass::Util.array_minus(engines, [self])
    end
def dependencies
      _dependencies(Set.new, engines = Set.new)
      Sass::Util.array_minus(engines, [self])
    end
Gets a set of all the documents
 that are (transitive) dependencies of this document,
 not including the document itself.

 @return [[Sass::Engine]] The dependency documents.