```Python
say_hi(name=None)  # This works, None is valid 🎉
```

The good news is, once you are on Python 3.10 you won't have to worry about that, as you will be able to simply use `|` to define unions of types:

{* ../../docs_src/python_types/tutorial009c_py310.py hl[1,4] *}

And then you won't have to worry about names like `Optional` and `Union`. 😎

#### Generic types { #generic-types }

/// note | Nota

//
// Note that returning an error here will cause the Metrics handler to return a
// 500 Internal Server Error.
type MetricsLoaderFn func(context.Context, MetricValues, *metricsCache) error

// JoinLoaders - joins multiple loaders into a single loader. The returned
// loader will call each of the given loaders in order. If any of the loaders
// return an error, the returned loader will return that error.

		result := drain(input)
		if result != test.output {
			t.Errorf("%s: got %q expected %q", test.name, result, test.output)
		}
	}
}

// lines joins the arguments together as complete lines.
func lines(a ...string) string {
	return strings.Join(a, "\n") + "\n"
}

// drain returns a single string representing the processed input tokens.

/// note

Ao definir um <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a>, inclua o tipo mais específico primeiro, seguido pelo tipo menos específico. No exemplo abaixo, o tipo mais específico `PlaneItem` vem antes de `CarItem` em `Union[PlaneItem, CarItem]`.

/// note | Примечание

При объявлении <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a>, сначала указывайте наиболее детальные типы, затем менее детальные. В примере ниже более детальный `PlaneItem` стоит перед `CarItem` в `Union[PlaneItem, CarItem]`.

///

						}
					} else if names := utils.SplitNestedRelationName(column); len(names) > 1 { // has nested relation
						aliasName := utils.JoinNestedRelationNames(names[0 : len(names)-1])
						for _, join := range db.Statement.Joins {
							if join.Alias == aliasName {
								names = append(strings.Split(join.Name, "."), names[len(names)-1])
								break
							}
						}

						if rel, ok := sch.Relationships.Relations[names[0]]; ok {

/// note | Hinweis

```Python
say_hi(name=None)  # Dit werkt, None is geldig 🎉
```

Het goede nieuws is dat als je eenmaal Python 3.10 gebruikt, je je daar geen zorgen meer over hoeft te maken, omdat je dan gewoon `|` kunt gebruiken om unions van types te definiëren:

{* ../../docs_src/python_types/tutorial009c_py310.py hl[1,4] *}


Dan hoef je je geen zorgen te maken over namen als `Optional` en `Union`. 😎

#### Generieke typen

		t.Fatalf("Build count with select, but got %v", result.Statement.SQL.String())
	}

	var count4 int64
	if err := DB.Table("users").Joins("LEFT JOIN companies on companies.name = users.name").Where("users.name = ?", user1.Name).Count(&count4).Error; err != nil || count4 != 1 {
		t.Errorf("count with join, got error: %v, count %v", err, count4)
	}