These features are what Marshmallow was built to provide. It is a great library, and I have used it a lot before.

But it was created before there existed Python type hints. So, to define every <abbr title="the definition of how data should be formed">schema</abbr> you need to use specific utils and classes provided by Marshmallow.

/// check | Inspired **FastAPI** to

  public static <T extends @Nullable Object> Predicate<T> in(Collection<? extends T> target) {
    return new InPredicate<>(target);
  }

  /**
   * Returns the composition of a function and a predicate. For every {@code x}, the generated
   * predicate returns {@code predicate(function(x))}.
   *
   * @return the composition of the provided function and predicate
   */

<p>
The built-in functions <code>append</code> and <code>copy</code> assist in
common slice operations.
For both functions, the result is independent of whether the memory referenced
by the arguments overlaps.
</p>

<p>
The <a href="#Function_types">variadic</a> function <code>append</code>
appends zero or more values <code>x</code> to a slice <code>s</code> of

 */
public abstract class Converter<A, B> implements Function<A, B> {
  private final boolean handleNullAutomatically;

  // We lazily cache the reverse view to avoid allocating on every call to reverse().
  @LazyInit @RetainedWith private transient @Nullable Converter<B, A> reverse;

  /** Constructor for use by subclasses. */
  protected Converter() {
    this(true);
  }

      return delegate.isCancelled();
    }
  }

  /**
   * A {@link Scheduler} that provides a convenient way for the {@link AbstractScheduledService} to
   * use a dynamically changing schedule. After every execution of the task, assuming it hasn't been
   * cancelled, the {@link #getNextSchedule} method will be called.
   *
   * @author Luke Sandberg
   * @since 11.0
   */

    connections.

 *  Fix: Immediately update the connection's flow control window instead of waiting for the
    receiving stream to process it.

    This change may increase OkHttp's memory use for applications that make many concurrent HTTP
    calls and that can receive data faster than they can process it. Previously, OkHttp limited

)

// Temp files created in default Tmp dir
var globalTestTmpDir = os.TempDir()

// reseed - returns a new seed every time the function is called.
func reseed() uint32 {
	return uint32(time.Now().UnixNano() + int64(os.Getpid()))
}

// nextSuffix - provides a new unique suffix every time the function is called.
func nextSuffix() string {
	randmu.Lock()
	r := randN
	// Initial seed required, generate one.

     * other networking protocols the InputStream may need
     * to be passed to the readXxxWireFormat methods. This is
     * actually purer. However, in the case of smb we know the
     * wordCount and byteCount. And since every subclass of
     * ServerMessageBlock would have to perform the same read
     * operation on the input stream, we might as will pull that
     * common functionality into the superclass and read wordCount

	// used when o.Versioned is false
	if !o.Versioned {
		resolver.requestedVersions = 1
	}
	var limit int
	if o.Limit > 0 && o.StopDiskAtLimit {
		// Over-read by 4 + 1 for every 16 in limit to give some space for resolver,
		// allow for truncating the list and know if we have more results.
		limit = o.Limit + 4 + (o.Limit / 16)
	}
	ctxDone := ctx.Done()

	curr fileReader // Reader for current file entry
	blk  block      // Buffer to use as temporary local storage

	// err is a persistent error.
	// It is only the responsibility of every exported method of Reader to
	// ensure that this error is sticky.
	err error
}

type fileReader interface {
	io.Reader
	fileState

	WriteTo(io.Writer) (int64, error)
}