code: def _validate_namespaces(self, input_namespaces):
          
          output_namespaces = []
          if input_namespaces == []:
              return output_namespaces
          elif '*' in input_namespaces:
              if len(input_namespaces) > 1:
                  warning = 'Warning: Multiple namespaces are '
                  warning += 'ignored when one namespace is "*"\n'
                  sys.stderr.write(warning)
              return output_namespaces
          else:
              for namespace in input_namespaces:
                  if not isinstance(namespace, unicode):
                      namespace = unicode(namespace)
                  namespace_tuple = self._tuplefy_namespace(namespace)
                  if namespace_tuple is None:
                      warning = 'Warning: Invalid namespace ' + namespace
                      warning += ' will be ignored\n'
                      sys.stderr.write(warning)
                  else:
                      if namespace_tuple not in output_namespaces:
                          output_namespaces.append(namespace_tuple)
                      else:
                          warning = 'Warning: Duplicate namespace ' + namespace
                          warning += ' will be ignored\n'
                          sys.stderr.write(warning)
          return output_namespaces
docs: Converts a list of db namespaces to a list of namespace tuples,
              supporting basic commandline wildcards