code: public static String getPrefix(String namespaceString)
      {
          Namespace namespace = toNamespace(namespaceString);
  
          return namespace != null ? namespace.getType() : null;
      }
docs: Extract prefix of the id used to find custom factory.
  
  @param namespaceString the namespace as a {@link String}
  @return the type of the namespace or null if none is provided