{!> ../../docs_src/dependencies/tutorial008.py!}
```

////

And all of them can use `yield`.

In this case `dependency_c`, to execute its exit code, needs the value from `dependency_b` (here named `dep_b`) to still be available.

And, in turn, `dependency_b` needs the value from `dependency_a` (here named `dep_a`) to be available for its exit code.

//// tab | Python 3.9+

```Python hl_lines="18-19  26-27"

// indicates readDirFn to return without further applying the fn()
var errDoneForNow = errors.New("done for now")

// errSkipFile returned by the fn() for readDirFn() when it needs
// to proceed to next entry.
var errSkipFile = errors.New("skip this file")

var errIgnoreFileContrib = errors.New("ignore this file's contribution toward data-usage")

	if err := meta.load(ctx, z.serverPools[0], z.serverPools); err != nil {
		return err
	}

	update, err := meta.validate(z.serverPools)
	if err != nil {
		return err
	}

	// if no update is needed return right away.
	if !update {
		z.poolMetaMutex.Lock()
		z.poolMeta = meta
		z.poolMetaMutex.Unlock()
	} else {
		newMeta := newPoolMeta(z, meta)
		if err = newMeta.save(ctx, z.serverPools); err != nil {

      entries[srcIndex] = UNSET;

      // also need to update whoever's "next" pointer was pointing to the last entry place
      // reusing "tableIndex" and "next"; these variables were no longer needed
      int tableIndex = getHash(lastEntry) & hashTableMask();
      int lastNext = table[tableIndex];
      if (lastNext == srcIndex) {
        // we need to update the root pointer
        table[tableIndex] = dstIndex;

	if prefix == "" {
		// if all objects are not deleted yet this call may fail.
		return clnt.RemoveBucket(cctx, bucket)
	}

	objectsCh := make(chan minio.ObjectInfo)

	// Send object names that are needed to be removed to objectsCh
	go func() {
		defer xioutil.SafeClose(objectsCh)
		opts := minio.ListObjectsOptions{
			Prefix:    prefix,
			Recursive: true,
		}

	globalTierConfigMgr *TierConfigMgr

	globalConsoleSrv *consoleapi.Server

	// handles service freeze or un-freeze S3 API calls.
	globalServiceFreeze atomic.Value

	// Only needed for tracking
	globalServiceFreezeCnt int32
	globalServiceFreezeMu  sync.Mutex // Updates.

	// Map of local drives to this node, this is set during server startup,

 * 
 * We strongly suggest that you create an explicit {@link jcifs.context.CIFSContextWrapper}
 * with your desired config. It's base implementation {@link jcifs.context.BaseContext}
 * should be sufficient for most needs.
 * 
 * If you want to retain the classic singleton behavior you can use
 * {@link jcifs.context.SingletonContext#getInstance()}
 * witch is initialized using system properties.
 * 
 */
@SuppressWarnings ( "javadoc" )

                }
            }
            if (targetInformation != null) {
                flags |= NTLMSSP_NEGOTIATE_TARGET_INFO;
                // empty context is needed for padding when t.i. is supplied.
                if (context == null) context = new byte[8];
            }
            int data = 32;
            if (context != null) data += 8;

///

### Add the callback router

At this point you have the *callback path operation(s)* needed (the one(s) that the *external developer*  should implement in the *external API*) in the callback router you created above.

// Blocks will read this much and find the first following newline.
// 128KB appears to be a very reasonable default.
const csvSplitSize = 128 << 10

// startReaders will read the header if needed and spin up a parser
// and a number of workers based on GOMAXPROCS.
// If an error is returned no goroutines have been started and r.err will have been set.