The same would happen if you had something like a <abbr title='A union between multiple types means "any of these types".'>union</abbr> between different types where one or more of them are not valid Pydantic types, for example this would fail 💥:

//// tab | Python 3.10+

```Python hl_lines="8"

 * Response caching avoids the network completely for repeat requests.

OkHttp perseveres when the network is troublesome: it will silently recover from common connection
problems. If your service has multiple IP addresses, OkHttp will attempt alternate addresses if the
first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data

     * this client silently recovers from the following problems:
     *
     * * **Unreachable IP addresses.** If the URL's host has multiple IP addresses,
     *   failure to reach any individual IP address doesn't fail the overall request. This can
     *   increase availability of multi-homed services.
     *

    if not fields:
        return False
    # More than one dependency could have the same field, it would show up as multiple
    # fields but it's the same one, so count them by name
    body_param_names_set = {field.name for field in fields}
    # A top level field has to be a single field, not multiple
    if len(body_param_names_set) > 1:
        return True
    first_field = fields[0]

	return &StreamTypeHandler[Payload, Req, Resp]{id: h, InCapacity: 1, OutCapacity: 1}
}

// Register a handler for two-way streaming with payload, input stream and output stream.
// An optional subroute can be given. Multiple entries are joined with '/'.
func (h *StreamTypeHandler[Payload, Req, Resp]) Register(m *Manager, handle func(ctx context.Context, p Payload, in <-chan Req, out chan<- Resp) *RemoteErr, subroute ...string) error {

`Optional[str]` の`Optional` はFastAPIでは使用されていません（FastAPIは`str`の部分のみ使用します）。しかし、`Optional[str]` はエディタがコードのエラーを見つけるのを助けてくれます。

///

## Pydanticを使わない方法

	maxRecordMessageLength = (128 << 10) - 256
)

var bufLength = payloadLenForMsgLen(maxRecordMessageLength)

// newRecordsMessage - creates new Records Message which can contain a single record, partial records,
// or multiple records. Depending on the size of the result, a response can contain one or more of these messages.
//
// Header specification
// Records messages contain three headers, as follows:

 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *
 * <p>This tests {@code foo.equals(foo)}, {@code foo.equals(null)}, and a few other operations.
 *
 * <p>For more extensive testing, add multiple equality groups. Each group should contain objects
 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>
 * new EqualsTester()

 * could in principle cause problems for some users. Still, we expect that the benefits of the
 * nullness annotations in particular will outweigh the costs. (And it's worth noting that we have
 * released multiple ListenableFuture.class files that are not byte-for-byte compatible even from
 * the beginning, thanks to using different `-source -target` values for compiling our `-jre` and
 * `-android` "flavors.")
 *

 * evicted or manually invalidated. The common way to build instances is using {@link CacheBuilder}.
 *
 * <p>Implementations of this interface are expected to be thread-safe, and can be safely accessed
 * by multiple concurrent threads.
 *
 * @param <K> the type of the cache's keys, which are not permitted to be null
 * @param <V> the type of the cache's values, which are not permitted to be null
 * @author Charles Fry
 * @since 10.0