// permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEY_QUERIES)
  public void testReplace_absentNullKeyUnsupported() {
    try {
      getMap().replace(null, v3());
    } catch (NullPointerException tolerated) {
      // permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

      // permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEY_QUERIES)
  public void testReplace_absentNullKeyUnsupported() {
    try {
      getMap().replace(null, v3());
    } catch (NullPointerException tolerated) {
      // permitted not to throw because it would be a no-op
    }
    expectUnchanged();
  }

Because we are using a relative URL, if your API was located at `https://example.com/`, then it would refer to `https://example.com/token`. But if your API was located at `https://example.com/api/v1/`, then it would refer to `https://example.com/api/v1/token`.

     * implement Function<A, B>, as discussed in a class-level comment), it would make some sense to
     * perform runtime null checks on the input and output. (That would also make NullPointerTester
     * happy!) However, since we didn't do that for many years, we're not about to start now.
     * (Runtime checks could be particularly bad for users of LegacyConverter.)
     *

We can do better...

## What makes a dependency { #what-makes-a-dependency }

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

A "**callable**" in Python is anything that Python can "call" like a function.

The way you use it is very simple. For example, to do a `GET` request, you would write:

```Python
response = requests.get("http://example.com/some/url")
```

The FastAPI counterpart API *path operation* could look like:

```Python hl_lines="1"
@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}
```

See the similarities in `requests.get(...)` and `@app.get(...)`.

In Pydantic version 1, you would use an internal class `Config` and `schema_extra`, as described in <a href="https://docs.pydantic.dev/1.10/usage/schema/#schema-customization" class="external-link" target="_blank">Pydantic's docs: Schema customization</a>.

You can set `schema_extra` with a `dict` containing any additional data you would like to show up in the generated JSON Schema, including `examples`.

////

/// tip

```

</div>

/// tip

With `passlib`, you could even configure it to be able to read passwords created by **Django**, a **Flask** security plug-in or many others.

So, you would be able to, for example, share the same data from a Django application in a database with a FastAPI application. Or gradually migrate a Django application using the same database.

    /**
     * Gets the relative path for a locally installed artifact.
     * Note that the artifact need not actually exist yet at
     * the returned location, the path merely indicates where
     * the artifact would eventually be stored.
     *
     * @param session The session to use, must not be {@code null}.
     * @param artifact The artifact for which to determine the path, must not be {@code null}.

   *     the size method
   */
  public static <T extends @Nullable Object> Collection<T> misleadingSizeCollection(int delta) {
    // It would be nice to be able to return a real concurrent
    // collection like ConcurrentLinkedQueue, so that e.g. concurrent
    // iteration would work, but that would not be GWT-compatible.
    // We are not "just" inheriting from ArrayList here as this doesn't work for J2kt.
    return new AbstractList<T>() {