# Classes as Dependencies

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example

In the previous example, we were returning a `dict` from our dependency ("dependable"):

//// tab | Python 3.10+

```Python hl_lines="9"
{!> ../../docs_src/dependencies/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="11"

	defer conn.Close()

	context.AfterFunc(ctx, func() {
		log.Debug("context cancelled, closing ztunnel server")
		conn.Close()
	})

	// before doing anything, add the connection to the list of active connections
	z.conns.addConn(conn)
	defer z.conns.deleteConn(conn)

	// get hello message from ztunnel

    for (int i = 0; i < length; i++) {
      checkElementNotNull(array[i], i);
    }
    return array;
  }

  // We do this instead of Preconditions.checkNotNull to save boxing and array
  // creation cost.
  @CanIgnoreReturnValue
  static Object checkElementNotNull(@CheckForNull Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);

        // subclass is implemented with bugs similar to the subclass.
        pendingDescription = "Exception thrown from implementation: " + e.getClass();
      }
      // The future may complete during or before the call to getPendingToString, so we use null
      // as a signal that we should try checking if the future is done again.
      if (!isNullOrEmpty(pendingDescription)) {

}

// Return shuffled partsMetadata depending on fi.Distribution.
// additional validation is attempted and invalid metadata is
// automatically skipped only when fi.ModTime is non-zero
// indicating that this is called during read-phase
func shuffleDisksAndPartsMetadata(disks []StorageAPI, partsMetadata []FileInfo, fi FileInfo) (shuffledDisks []StorageAPI, shuffledPartsMetadata []FileInfo) {
	shuffledDisks = make([]StorageAPI, len(disks))

        }
    }

    /**
     * Ensures the last updated timestamp of the specified metadata does not refer to the future and fixes the local
     * metadata if necessary to allow proper merging/updating of metadata during deployment.
     */
    private void fixTimestamp(File metadataFile, Metadata metadata, Metadata reference) {
        boolean changed = false;

        if (metadata != null && reference != null) {

        }

        // Check for identity or widening reference conversion
        if (actual != null && formal.isAssignableFrom(actual)) {
            return true;
        }

        // Check for boxing with widening primitive conversion. Note that
        // actual parameters are never primitives.
        if (formal.isPrimitive()) {
            if (formal == Boolean.TYPE && actual == Boolean.class) {

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  //
  // Otherwise if all of the tensors have the same shape, returns that via the
  // `shape` output argument. This blocks waiting for async tensors, may return
  // a delayed bad status encountered during async execution, and will return a
  // bad status unless all tensors have the same shape.
  absl::Status Shape(const std::vector<int64_t>** shape) const;
  TF_DataType dtype() const { return dtype_; }

        List<ArtifactRepository> pomRepositories = null;

        Artifact pomArtifact;

        Artifact relocatedArtifact = null;

        // TODO hack: don't rebuild model if it was already loaded during reactor resolution
        RepositorySystemSession repositorySession = legacySupport.getRepositorySession();
        final WorkspaceReader workspace = repositorySession.getWorkspaceReader();
        Model model;