code: public static boolean isSupportedSchema(Schema s) {
      Schema.Type typ =  s.getType();
      switch (typ) {
        case BOOLEAN:
        case INT:
        case LONG:
        case FLOAT:
        case DOUBLE:
        case ENUM:
        case STRING:
        case NULL:
        case BYTES:
          return true;
        case UNION: // Flattenize the union
          List<Schema> unionSchemas = s.getTypes();
          if (unionSchemas.size() == 1) {
            return isSupportedSchema(unionSchemas.get(0));
          } else if (unionSchemas.size() == 2) {
            Schema s1 = unionSchemas.get(0);
            Schema s2 = unionSchemas.get(1);
            return s1.getType().equals(Schema.Type.NULL) && isSupportedSchema(s2)
                   || s2.getType().equals(Schema.Type.NULL) && isSupportedSchema(s1);
          }
        default:
          return false;
      }
    }
docs: Return true if the given schema can be transformed
  into h2o type.
  
  @param s  avro field schema
  @return  true if the schema can be transformed into H2O type