) -> Type[BaseModel]:
        field_params = {f.name: (f.field_info.annotation, f.field_info) for f in fields}
        BodyModel: Type[BaseModel] = create_model(model_name, **field_params)  # type: ignore[call-overload]
        return BodyModel

    def get_model_fields(model: Type[BaseModel]) -> List[ModelField]:
        return [
            ModelField(field_info=field_info, name=name)

// The permission bits perm (before umask) are used for all
// directories that MkdirAll creates.
// If path is already a directory, MkdirAll does nothing
// and returns nil.
func osMkdirAll(dirPath string, perm os.FileMode, baseDir string) error {
	if baseDir != "" {
		if strings.HasPrefix(baseDir, dirPath) {
			return nil
		}
	}

	// Slow path: make sure parent exists and then call Mkdir for path.
	i := len(dirPath)

```

This behavior is consistent across all keys; each key self-documents itself with valid examples.

## Dynamic systems without restarting server

The following sub-systems are dynamic i.e., configuration parameters for each sub-systems can be changed while the server is running without any restarts.

```
api                   manage global HTTP API call specific features, such as throttling, authentication types, etc.

	db := DB.Scopes(func(tx *gorm.DB) *gorm.DB {
		return tx.Table("custom_table")
	}).Session(&gorm.Session{})

	db.AutoMigrate(&User{})
	if db.Find(&User{}).Statement.Table != "custom_table" {
		t.Errorf("failed to call Scopes")
	}

	result := DB.Scopes(NameIn1And2, func(tx *gorm.DB) *gorm.DB {
		return tx.Session(&gorm.Session{})
	}).Find(&users1)

	if result.RowsAffected != 2 {

```

////

/// tip

All this might seem contrived. And it might not be very clear how is it useful yet.

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

  float* values = new float[1];
  values[0] = v;
  return TF_NewTensor(TF_FLOAT, nullptr, 0, values, num_bytes,
                      &FloatDeallocator, nullptr);
}

// All the *Helper methods are used as a workaround for the restrictions that
// one cannot call ASSERT_* methods in non-void-returning functions (when
// exceptions are disabled during compilation)
void PlaceholderHelper(TF_Graph* graph, TF_Status* s, const char* name,

  // clients from directly destroying this object since it may manage it's own
  // lifetime through ref counting. Thus this must be allocated on the heap and
  // clients MUST call Release() in order to destroy an instance of this class.
  virtual void Release() = 0;

  virtual absl::Status Reset(const char* op, const char* raw_device_name) = 0;

  virtual const string& Name() const = 0;

```Python hl_lines="1  10"
{!> ../../docs_src/settings/app03/main.py!}
```

////

Then for any subsequent call of `get_settings()` in the dependencies for the next requests, instead of executing the internal code of `get_settings()` and creating a new `Settings` object, it will return the same object that was returned on the first call, again and again.

#### `lru_cache` Technical Details

times for the same *path operation*, for example, multiple dependencies have a common sub-dependency, **FastAPI** will know to call that sub-dependency only once per request.

And it will save the returned value in a <abbr title="A utility/system to store computed/generated values, to reuse them instead of computing them again.">"cache"</abbr> and pass it to all the "dependants" that need it in that specific request, instead of calling the dependency multiple times for the same request....

// An Update function must be set to provide an updated value when needed.
type Cache[T any] struct {
	// updateFn must return an updated value.
	// If an error is returned the cached value is not set.
	// Only one caller will call this function at any time, others will be blocking.
	// The returned value can no longer be modified once returned.
	// Should be set before calling Get().
	updateFn func(ctx context.Context) (T, error)