@Override
  public UnboundFunction loadFunction(Identifier ident) throws NoSuchFunctionException {

    TableCatalog tableCatalog = tableCatalog(TableFormat.ICEBERG);
    if (tableCatalog instanceof FunctionCatalog) {
      return ((FunctionCatalog) tableCatalog).loadFunction(ident);
    }
    throw new NoSuchFunctionException(ident);
  }
Load a function by {@link Identifier identifier} from the catalog.

@param ident a function identifier
@return an unbound function instance
@throws NoSuchFunctionException If the function doesn't exist
amoro-format-mixed/amoro-mixed-spark/v3.5/amoro-mixed-spark-3.5/src/main/java/org/apache/amoro/spark/SparkUnifiedCatalog.java