An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

This provider might be charging you per request, and calling it might take some extra time than if you had a fixed mock user for tests.

You probably want to test the external provider once, but not necessarily call it for every test that runs.

# Sub-dependencies

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable"

You could create a first dependency ("dependable") like:

//// tab | Python 3.10+

```Python hl_lines="8-9"
{!> ../../docs_src/dependencies/tutorial005_an_py310.py!}
```

////

//// tab | Python 3.9+

		// Leader node (that successfully acquires the lock inside runCallhome)
		// will keep performing the callhome. If the leader goes down for some reason,
		// the lock will be released and another node will acquire it and take over
		// because of this loop.
		for {
			if !globalCallhomeConfig.Enabled() {
				return
			}

			if !runCallhome(ctx, objAPI) {
				// callhome was disabled or context was canceled
				return
			}

# Python Types Intro

Python has support for optional "type hints" (also called "type annotations").

These **"type hints"** or annotations are a special syntax that allow declaring the <abbr title="for example: str, int, float, bool">type</abbr> of a variable.

By declaring types for your variables, editors and tools can give you better support.

	}
	AssertEqual(t, find1, value)
}

func TestEmbedPreload(t *testing.T) {
	type Country struct {
		ID   int `gorm:"primaryKey"`
		Name string
	}
	type EmbeddedAddress struct {
		ID        int
		Name      string
		CountryID *int
		Country   *Country
	}
	type NestedAddress struct {
		EmbeddedAddress
	}
	type Org struct {
		ID              int

			agreed: func(entry metaCacheEntry) {
				jt.Take()
				go healEntry(bucket, entry)
			},
			partial: func(entries metaCacheEntries, _ []error) {
				entry, ok := entries.resolve(&resolver)
				if !ok {
					// check if we can get one entry at least
					// proceed to heal nonetheless.
					entry, _ = entries.firstFound()
				}
				jt.Take()
				go healEntry(bucket, *entry)
			},

    theta_inputs[input_index] = thetaMinus.get();
    TF_RETURN_IF_ERROR(
        RunAndMaybeSum(ctx, forward, theta_inputs, f_outputs, use_function));
    AbstractTensorHandlePtr fMinus(f_outputs[0]);

    // Take Difference of both estimates: (f(theta + eps) - f(theta - eps)).
    TF_RETURN_IF_ERROR(
        ops::Sub(ctx, fPlus.get(), fMinus.get(), f_outputs, "sub_top"));
    AbstractTensorHandlePtr fDiff(f_outputs[0]);

   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain
   * ParametricNullness parametric nullness}. If a type parameter instead ranges over only non-null
   * types (or if the type is a non-variable type, like {@code String}), then code should almost
   * never use this method, preferring instead to call {@code requireNonNull} so as to benefit from

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  professional setting

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