import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.function.BiConsumer;

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrInvalidQuoteFields: {
		Code:           "InvalidQuoteFields",
		Description:    "The QuoteFields is invalid. Only ALWAYS and ASNEEDED are supported.",
		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrInvalidRequestParameter: {
		Code:           "InvalidRequestParameter",

var unionWithPointer = make(map[ast.Expr]bool)

// anonymousStructTag provides a consistent tag for an anonymous struct.
// The same dwarf.StructType pointer will always get the same tag.
var anonymousStructTag = make(map[*dwarf.StructType]string)

func (c *typeConv) Init(ptrSize, intSize int64) {
	c.ptrSize = ptrSize
	c.intSize = intSize
	c.m = make(map[string]*Type)

			}
			if !bytes.Equal(buf, all[i:i+j]) {
				t.Errorf("ReadAt(%d, %d) = %q; want %q", i, j, buf, all[i:i+j])
			}
		}
	}
}

// fakeHash32 is a dummy Hash32 that always returns 0.
type fakeHash32 struct {
	hash.Hash32
}

func (fakeHash32) Write(p []byte) (int, error) { return len(p), nil }
func (fakeHash32) Sum32() uint32               { return 0 }

	otags := &objectTagging{
		TagSet: &ObjectTagSet{},
	}

	var list []tags.Tag
	for k, v := range ot.ToMap() {
		list = append(list, tags.Tag{
			Key:   k,
			Value: v,
		})
	}
	// Always return in sorted order for tags.
	sort.Slice(list, func(i, j int) bool {
		return list[i].Key < list[j].Key
	})
	otags.TagSet.Tags = list

	writeSuccessResponseXML(w, encodeResponse(otags))
}

		return
	}
	opts.Versioned = versioned
	opts.VersionSuspended = suspended

	// First, we compute the ETag of the multipart object.
	// The ETag of a multi-part object is always:
	//   ETag := MD5(ETag_p1, ETag_p2, ...)+"-N"   (N being the number of parts)
	//
	// This is independent of encryption. An encrypted multipart
	// object also has an ETag that is the MD5 of its part ETags.

//
// The text returned from ReadLine does not include the line end ("\r\n" or "\n").
// No indication or error is given if the input ends without a final line end.
// Calling [Reader.UnreadByte] after ReadLine will always unread the last byte read
// (possibly a character belonging to the line end) even if that byte is not
// part of the line returned by ReadLine.
func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {

// subsystem (whether they are enabled or not). A target could be configured via
// environment variables or via the configuration store. The default target is
// `_` and is always returned. The result is sorted so that the default target
// is the first one and the remaining entries are sorted in ascending order.
func (c Config) GetAvailableTargets(subSys string) ([]string, error) {

    status->status = InvalidArgument("Invalid GraphDef");
    return;
  }
  status->status = s->session->Extend(g);
}

}  // end extern "C"

// Reset helper for converting character arrays to string vectors.
static void TF_Reset_Helper(const TF_SessionOptions* opt,
                            const char** containers, int ncontainers,
                            TF_Status* status) {