If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a *path operation function*. Including sub-dependencies.

That also applies to callables with no parameters at all. The same as it would be for *path operation functions* with no parameters.

**FastAPI** knows what to do in each case and how to reuse the same object, so that all the background tasks are merged together and are run in the background afterwards:


{* ../../docs_src/background_tasks/tutorial002_an_py310.py hl[13,15,22,25] *}

        when(mockChannelManager.getHealthyChannels()).thenReturn(Arrays.asList(channel1, channel2));

        // Multiple calls with same file ID should return same channel
        ChannelInfo first = loadBalancer.selectChannel(readRequest);
        ChannelInfo second = loadBalancer.selectChannel(readRequest);

        assertEquals(first, second);
    }

import junit.framework.TestCase;

/**
 * Test cases for {@code EventBus} that must not be in the same package.
 *
 * @author Louis Wasserman
 */
public class OutsideEventBusTest extends TestCase {

  /*
   * If you do this test from common.eventbus.EventBusTest, it doesn't actually test the behavior.
   * That is, even if exactly the same method works from inside the common.eventbus package tests,
   * it can fail here.
   */

  ]
}
```

because the path parameter `item_id` had a value of `"foo"`, which is not an `int`.

The same error would appear if you provided a `float` instead of an `int`, as in: <a href="http://127.0.0.1:8000/items/4.2" class="external-link" target="_blank">http://127.0.0.1:8000/items/4.2</a>

/// check

So, with the same Python type declaration, **FastAPI** gives you data validation.

        assertNull(session.transport, "transport not created yet");
        SmbTransport tr = session.transport();
        assertNotNull(tr, "transport should now exist");
        // subsequent calls return the same instance
        assertSame(tr, session.transport());
    }

    @Test
    void sendResetsResponseAndForwards() throws Exception {
        SmbSession session = new SmbSession(addr, 445, inet, 0, auth);

### Environment variables

#### MINIO_ETCD_ENDPOINTS

This is comma separated list of etcd servers that you want to use as the MinIO federation back-end. This should
be same across the federated deployment, i.e. all the MinIO instances within a federated deployment should use same
etcd back-end.

#### MINIO_DOMAIN

This is the top level domain name used for the federated setup. This domain name should ideally resolve to a load-balancer

    }

    @Test
    @DisplayName("getSmbTree returns same instance for same share/service")
    void testGetSmbTreeReuses() {
        SmbSessionImpl session = newSession();
        SmbTreeImpl t1 = session.getSmbTree("IPC$", null);
        SmbTreeImpl t2 = session.getSmbTree("ipc$", null); // case-insensitive match
        assertSame(t1, t2, "Expected same tree instance to be reused");
    }

    @ParameterizedTest

The same as when using a custom CDN, the first step is to disable the automatic docs, as those use the CDN by default.

To disable them, set their URLs to `None` when creating your `FastAPI` app:

{* ../../docs_src/custom_docs_ui/tutorial002.py hl[9] *}

### Include the custom docs for static files { #include-the-custom-docs-for-static-files }

You can use the same dependency *functions* you use normally.

### Dependency requirements { #dependency-requirements }

They can declare request requirements (like headers) or other sub-dependencies:

{* ../../docs_src/dependencies/tutorial006_an_py39.py hl[8,13] *}

### Raise exceptions { #raise-exceptions }

These dependencies can `raise` exceptions, the same as normal dependencies: