code: public static Type array(Type elementType) {
      Preconditions.checkNotNull(elementType);
      switch (elementType.getCode()) {
        case BOOL:
          return TYPE_ARRAY_BOOL;
        case INT64:
          return TYPE_ARRAY_INT64;
        case FLOAT64:
          return TYPE_ARRAY_FLOAT64;
        case STRING:
          return TYPE_ARRAY_STRING;
        case BYTES:
          return TYPE_ARRAY_BYTES;
        case TIMESTAMP:
          return TYPE_ARRAY_TIMESTAMP;
        case DATE:
          return TYPE_ARRAY_DATE;
        default:
          return new Type(Code.ARRAY, elementType, null);
      }
    }
docs: Returns a descriptor for an array of {@code elementType}.