if (value instanceof final LocalDateTime ldt) {
            final ZonedDateTime zdt = ZonedDateTime.of(ldt, ZoneId.systemDefault());
            super.addFieldToSource(sourceMap, field, DateTimeFormatter.ISO_INSTANT.format(zdt));
        } else {
            super.addFieldToSource(sourceMap, field, value);
        }
    }

    @Override

        if (value instanceof final LocalDateTime ldt) {
            final ZonedDateTime zdt = ZonedDateTime.of(ldt, ZoneId.systemDefault());
            super.addFieldToSource(sourceMap, field, DateTimeFormatter.ISO_INSTANT.format(zdt));
        } else {
            super.addFieldToSource(sourceMap, field, value);
        }
    }

    @Override

</div>

This means that it will **always have a value**, it's just that sometimes the value could be `None` (or `null` in JSON).

That means that, clients using your API don't have to check if the value exists or not, they can **assume the field will always be there**, but just that in some cases it will have the default value of `None`.

// Singleton contains a pointer to T that must be set once.
// Until the value is set all Get() calls will block.
type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v
}

                                            <la:option value="25">25</la:option>
                                            <la:option value="50">50</la:option>
                                            <la:option value="100">100</la:option>
                                            <la:option value="200">500</la:option>
                                            <la:option value="1000">1000</la:option>

                return (T) value;
            }
            return (T) Long.valueOf(value.toString());
        }
        if (clazz.isAssignableFrom(Integer.class)) {
            if (value instanceof Integer) {
                return (T) value;
            }
            return (T) Integer.valueOf(value.toString());
        }
        if (clazz.isAssignableFrom(Double.class)) {

        <excludeScope implementation="java.lang.String" default-value="">${excludeScope}</excludeScope>
        <includeScope implementation="java.lang.String" default-value="runtime">${includeScope}</includeScope>
        <excludeGroupIds implementation="java.lang.String" default-value="">${excludeGroupIds}</excludeGroupIds>
        <skip implementation="boolean" default-value="false">${remoteresources.skip}</skip>

		<antcall target="install.module">
			<param name="repo.url" value="${maven.release.repo.url}" />
			<param name="module.groupId" value="org/codelibs/opensearch/module" />
			<param name="module.name.prefix" value="" />
			<param name="module.name" value="analysis-common" />
			<param name="module.version" value="${opensearch.version}" />
			<param name="module.zip.version" value="${opensearch.version}" />
		</antcall>
		<!-- geo -->

    assertThat(parse(url, "a=\r\t \n")!!.value).isEqualTo("")
  }

  @Test fun trimLeadingAndTrailingWhitespaceFromValue() {
    assertThat(parse(url, "a= ")!!.value).isEqualTo("")
    assertThat(parse(url, "a= b")!!.value).isEqualTo("b")
    assertThat(parse(url, "a=b ")!!.value).isEqualTo("b")
    assertThat(parse(url, "a=\r\t \nb\n\t \n")!!.value).isEqualTo("b")
  }

  @Test fun invalidCharacters() {

    checkArgument(
        value.signum() >= 0 && value.bitLength() <= Long.SIZE,
        "value (%s) is outside the range for an unsigned long value",
        value);
    return fromLongBits(value.longValue());
  }

  /**
   * Returns an {@code UnsignedLong} holding the value of the specified {@code String}, parsed as an
   * unsigned {@code long} value.
   *