## Dependencies

We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

We will now use a simple dependency to read a custom `X-Token` header:

//// tab | Python 3.9+

```Python hl_lines="3  6-8" title="app/dependencies.py"

        task = null;
        localTask.run();
        return;
      }
      // Executor called reentrantly! Make sure that further calls don't overflow stack. Further
      // reentrant calls will see that their current thread is the same as the one set in
      // latestTaskQueue, and queue rather than calling execute() directly.
      ThreadConfinedTaskQueue executingTaskQueue = new ThreadConfinedTaskQueue();

}

// supportedMACs specifies a default set of MAC algorithms in preference order.
// This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed
// because they have reached the end of their useful life.
// https://cs.opensource.google/go/x/crypto/+/refs/tags/v0.22.0:ssh/common.go;l=85
var supportedMACs = []string{

// ListOptions is the query options to a standard REST list call.
message ListOptions {
  // A selector to restrict the list of returned objects by their labels.
  // Defaults to everything.
  // +optional
  optional string labelSelector = 1;

  // A selector to restrict the list of returned objects by their fields.
  // Defaults to everything.
  // +optional
  optional string fieldSelector = 2;

        All that, on top of all the incredible help provided by a bunch of community members, the [FastAPI Experts](https://fastapi.tiangolo.com/fastapi-people/#experts), that give a lot of their time to come here and help others.

        That's a lot of work they are doing, but if more FastAPI users came to help others like them just a little bit more, it would be much less effort for them (and you and me 😅).

if [[ -n "$(which grealpath)" ]] &&  [[ -n "$(which gstat)" ]]; then
  alias realpath=grealpath
  alias stat=gstat
  # By default, aliases are only expanded in interactive shells, which means
  # that they are not substituted for their corresponding commands in shell
  # scripts. By setting "expand_aliases", we enable alias expansion in
  # non-interactive shells as well.
  shopt -s expand_aliases
else

      val maxAgeSecondsLong = timeUnit.toSeconds(maxAge.toLong())
      this.maxAgeSeconds = maxAgeSecondsLong.commonClampToInt()
    }

    /**
     * Accept cached responses that have exceeded their freshness lifetime by up to `maxStale`. If
     * unspecified, stale cache responses will not be used.
     *
     * @param maxStale a non-negative integer. This is stored and transmitted with

   * be called.
   */
  abstract boolean isDone();

  /**
   * Do interruptible work here - do not complete Futures here, as their listeners could be
   * interrupted.
   */
  @ParametricNullness
  abstract T runInterruptibly() throws Exception;

  /**

   * lies outside that, then {@link #escapeUnsafe} is called, otherwise no escaping is performed.
   *
   * @param replacementMap a map of characters to their escaped representations
   * @param safeMin the lowest character value in the safe range
   * @param safeMax the highest character value in the safe range

 * }</pre>
 *
 * @author Louis Wasserman
 * @since 15.0
 * @deprecated Use {@link com.google.common.graph.Traverser} instead. All instance methods have
 *     their equivalent on the result of {@code Traverser.forTree(tree)} where {@code tree}
 *     implements {@code SuccessorsFunction}, which has a similar API as {@link #children} or can be