code: public void xmlns(Map<String, String> definition) {
          Assert.notNull(namespaceHandlerResolver, "You cannot define a Spring namespace without a [namespaceHandlerResolver] set");
          if (definition.isEmpty()) {
              return;
          }
  
          for (Map.Entry<String, String> entry : definition.entrySet()) {
              String namespace = entry.getKey();
              String uri = entry.getValue() == null ? null : entry.getValue();
  
              Assert.notNull(uri, "Namespace definition cannot supply a null URI");
  
              final NamespaceHandler namespaceHandler = namespaceHandlerResolver.resolve(uri);
              if (namespaceHandler == null) {
                  throw new BeanDefinitionParsingException(
                        new Problem("No namespace handler found for URI: " + uri,
                              new Location(readerContext.getResource())));
              }
              namespaceHandlers.put(namespace, namespaceHandler);
              namespaces.put(namespace, uri);
          }
      }
docs: Defines a Spring namespace definition to use.
  
  @param definition The definition