if ev.Kind() == EventTaskBegin {
			task.Start = ev
		} else {
			task.End = ev
		}
		// Initialize the parent, if one exists and it hasn't been done yet.
		// We need to avoid doing it twice, otherwise we could appear twice
		// in the parent's Children list.
		if t.Parent != NoTask && task.Parent == nil {
			parent := s.getOrAddTask(t.Parent)
			task.Parent = parent

	// toolchain version during the toolchain switch by the parent
	// process and cleared in the child process. When set, that indicates
	// to the child to confirm that it provides the expected toolchain version.
	targetEnv = "GOTOOLCHAIN_INTERNAL_SWITCH_VERSION"

	// countEnv is a special environment variable
	// that is incremented during each toolchain switch, to detect loops.

			return n, err
		}
	}
	return
}

// Discard is a [Writer] on which all Write calls succeed
// without doing anything.
var Discard Writer = discard{}

type discard struct{}

// discard implements ReaderFrom as an optimization so Copy to
// io.Discard can avoid doing unnecessary work.
var _ ReaderFrom = discard{}

func (discard) Write(p []byte) (int, error) {
	return len(p), nil
}

3. This `yield from` tells the function to iterate over that thing named `file_like`. And then, for each part iterated, yield that part as coming from this generator function.

    So, it is a generator function that transfers the "generating" work to something else internally.

    By doing it this way, we can put it in a `with` block, and that way, ensure that it is closed after finishing.

!!! tip

calls. While in general the number of recursive calls can change the time
analysis, in this case doing three calls does not change the analysis:

	T(n) = 3T(n/2) + O(n) + O(n^log₂3)

ends up being T(n) = O(n^log₂3). Because the Karatsuba multiplication taking
time O(n^log₂3) is itself doing 3 half-sized recursions, doing three for the
division does not hurt the asymptotic performance. Of course, it is likely

	mp := acquirem()

	// Acquire the trace seqlock. This prevents traceAdvance from moving forward
	// until all Ms are observed to be outside of their seqlock critical section.
	//
	// Note: The seqlock is mutated here and also in traceCPUSample. If you update
	// usage of the seqlock here, make sure to also look at what traceCPUSample is
	// doing.
	seq := mp.trace.seqlock.Add(1)
	if debugTraceReentrancy && seq%2 != 1 {

	// treat "dead" writes as equivalent to reads during the analysis;
	// used only during liveness analysis for stack slot merging (doesn't
	// make sense for stackmap analysis).
	conservativeWrites bool
}

// Map maps from *ssa.Value to StackMapIndex.
// Also keeps track of unsafe ssa.Values and ssa.Blocks.
// (unsafe = can't be interrupted during GC.)
type Map struct {
	Vals         map[ssa.ID]objw.StackMapIndex

// methods to stop working.
// Because file descriptors can be reused, the returned file descriptor may
// only be closed through the [File.Close] method of f, or by its finalizer during
// garbage collection. Otherwise, during garbage collection the finalizer
// may close an unrelated file descriptor with the same (reused) number.
//
// As an alternative, see the f.SyscallConn method.
func (f *File) Fd() uintptr {

This could be especially useful during testing, as it's very easy to override a dependency with your own custom settings.

### The config file

Coming from the previous example, your `config.py` file could look like:

```Python hl_lines="10"
{!../../../docs_src/settings/app02/config.py!}
```

		panic("tls: internal error: wrong nonce length")
	}
	aes, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}
	var aead cipher.AEAD
	if boring.Enabled {
		aead, err = boring.NewGCMTLS(aes)
	} else {
		boring.Unreachable()
		aead, err = cipher.NewGCM(aes)
	}
	if err != nil {
		panic(err)
	}

	ret := &prefixNonceAEAD{aead: aead}
	copy(ret.nonce[:], noncePrefix)