def prefixes
      ns = []
      each_attribute do |attribute|
        ns << attribute.name if attribute.prefix == 'xmlns'
      end
      if @element.document and @element.document.doctype
        expn = @element.expanded_name
        expn = @element.document.doctype.name if expn.size == 0
        @element.document.doctype.attributes_of(expn).each {
          |attribute|
          ns << attribute.name if attribute.prefix == 'xmlns'
        }
      end
      ns
    end
def prefixes
      ns = []
      each_attribute do |attribute|
        ns << attribute.name if attribute.prefix == 'xmlns'
      end
      if @element.document and @element.document.doctype
        expn = @element.expanded_name
        expn = @element.document.doctype.name if expn.size == 0
        @element.document.doctype.attributes_of(expn).each {
          |attribute|
          ns << attribute.name if attribute.prefix == 'xmlns'
        }
      end
      ns
    end
Returns an array of Strings containing all of the prefixes declared
 by this set of # attributes.  The array does not include the default
 namespace declaration, if one exists.
  doc = Document.new("<a xmlns='foo' xmlns:x='bar' xmlns:y='twee' "+
        "z='glorp' p:k='gru'/>")
  prefixes = doc.root.attributes.prefixes    #-> ['x', 'y']