# Sub-dependencies { #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" { #first-dependency-dependable }

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

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

        final boolean eoled = isEoled();
        runtime.registerData("eoled", eoled);
        if (eoled) {
            final String eolLink = fessConfig.getOnlineHelpEol();
            runtime.registerData("eolLink", getHelpUrl(eolLink));
        }
    }

    /**
     * Sets up search HTML data for a given action.
     *
     * @param action  The action to set up data for.

- Thread-local storage via `CrawlingParameterUtil`

**Resource Management**:
- `AutoCloseable` throughout
- `DeferredFileOutputStream` for large responses (temp files for >1MB)
- Connection pooling with limits
- Background temp file deletion via `FileUtil.deleteInBackground()`

**Fault Tolerance**:
- `FaultTolerantClient` wrapper (retry, circuit breaker)

    final ImmutableList<Timeout> timeouts;

    TimeoutsToUse(Timeout... timeouts) {
      this.timeouts = ImmutableList.copyOf(timeouts);
    }
  }

  /** Possible outcomes of calling any of the methods under test. */
  private enum Outcome {

    /** The method returned normally and is either void or returned true. */
    SUCCESS,

    /** The method returned false. */
    FAILURE,

      assertWrapsInterruptedException(expected);
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  /**
   * awaitFullGc() is not quite as reliable a way to ensure calling of a specific finalize method as
   * the more direct await* methods, but should be reliable enough in practice to avoid flakiness of
   * this test. (And if it isn't, we'd like to know about it first!)
   */

     * <p>
     * This builder provides a fluent API for setting the various properties of an XML node.
     * All properties are optional except for the node name, which must be set before calling
     * {@link #build()}.
     */
    class Builder {
        private String name;
        private String value;
        private String namespaceUri;
        private String prefix;

      }
      awaitUnchecked(barrier);
      assertThat(future.isDone()).isTrue();
      // inspect state and ensure it is correct!
      // asserts that all get calling threads received the same value
      Object result = Iterables.getOnlyElement(finalResults);
      if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        if (future.wasInterrupted()) {

      assertWrapsInterruptedException(expected);
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  /**
   * awaitFullGc() is not quite as reliable a way to ensure calling of a specific finalize method as
   * the more direct await* methods, but should be reliable enough in practice to avoid flakiness of
   * this test. (And if it isn't, we'd like to know about it first!)
   */

        return super.hookBefore(runtime);
    }

    /**
     * Hook method called after action execution completes.
     * <p>
     * This method performs cleanup operations by calling the parent hook.
     * </p>
     *
     * @param runtime the action runtime context
     */
    @Override
    public void hookFinally(final ActionRuntime runtime) {
        super.hookFinally(runtime);

```Python
class Cat:
    def __init__(self, name: str):
        self.name = name


fluffy = Cat(name="Mr Fluffy")
```

In this case, `fluffy` is an instance of the class `Cat`.

And to create `fluffy`, you are "calling" `Cat`.

So, a Python class is also a **callable**.

Then, in **FastAPI**, you could use a Python class as a dependency.