regex: Annotated[
        str | None,
        Doc(
            """
            RegEx pattern for strings.
            """
        ),
        deprecated(
            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
        ),
    ] = None,
    discriminator: Annotated[
        str | None,
        Doc(
            """

	// check for omitted fields
	zb0001Len := uint32(18)
	var zb0001Mask uint32 /* 18 bits */
	_ = zb0001Mask
	if z.PartIndices == nil {
		zb0001Len--
		zb0001Mask |= 0x2000
	}
	// variable map header, size zb0001Len
	err = en.WriteMapHeader(zb0001Len)
	if err != nil {
		return
	}

	// skip if no fields are to be emitted
	if zb0001Len != 0 {
		// write "ID"

 * href="http://www.unicode.org/glossary/#BMP_character">BMP characters</a>. It does not understand
 * <a href="http://www.unicode.org/glossary/#supplementary_code_point">supplementary Unicode code
 * points</a> in the range {@code 0x10000} to {@code 0x10FFFF} which includes the majority of
 * assigned characters, including important CJK characters and emoji.
 *
 * <p>Supplementary characters are <a

 * href="http://www.unicode.org/glossary/#BMP_character">BMP characters</a>. It does not understand
 * <a href="http://www.unicode.org/glossary/#supplementary_code_point">supplementary Unicode code
 * points</a> in the range {@code 0x10000} to {@code 0x10FFFF} which includes the majority of
 * assigned characters, including important CJK characters and emoji.
 *
 * <p>Supplementary characters are <a