code: def match(self, root, ns):
          
          tns = root.get('targetNamespace')
          if len(self.tns):
              matched = ( tns in self.tns )
          else:
              matched = 1
          itself = ( ns == tns )
          return ( matched and not itself )
docs: Match by I{targetNamespace} excluding those that
          are equal to the specified namespace to prevent
          adding an import to itself.
          @param root: A schema root.
          @type root: L{Element}