r.Lock()
	defer r.Unlock()
	// Search of tag key already exists in tags
	var updated bool
	for _, tag := range r.tags {
		if tag.Key == key {
			tag.Val = val
			updated = true
			break
		}
	}
	if !updated {
		// Append to the end of tags list
		r.tags = append(r.tags, KeyVal{key, val})
	}
	return r
}

// GetTags - returns the user defined tags
func (r *ReqInfo) GetTags() []KeyVal {

package replication

import (
	"encoding/xml"
)

// And - a tag to combine a prefix and multiple tags for replication configuration rule.
type And struct {
	XMLName xml.Name `xml:"And" json:"And"`
	Prefix  string   `xml:"Prefix,omitempty" json:"Prefix,omitempty"`
	Tags    []Tag    `xml:"Tag,omitempty" json:"Tag,omitempty"`
}

var errDuplicateTagKey = Errorf("Duplicate Tag Keys are not allowed")

// isEmpty returns true if Tags field is null

<img src="/img/tutorial/generate-clients/image05.png">

## FastAPI App with Tags

In many cases your FastAPI app will be bigger, and you will probably use tags to separate different groups of *path operations*.

For example, you could have a section for **items** and another section for **users**, and they could be separated by tags:

=== "Python 3.9+"

    ```Python hl_lines="21  26  34"

            <tag>
              <name>implSpec</name>
              <placement>X</placement>
            </tag>
            <tag>
              <name>jls</name>
              <placement>X</placement>
            </tag>
            <tag>
              <name>revised</name>
              <placement>X</placement>
            </tag>
            <tag>
              <name>spec</name>

    val request =
      Request.Builder()
        .url("https://square.com")
        .tag(Any::class, tag)
        .build()
    assertThat(request.tag<Any>()).isSameAs(tag)
    assertThat(request.tag(Any::class)).isSameAs(tag)
    assertThat(request.tag(String::class)).isNull()

    // Alternate access APIs also work.
    assertThat(request.tag(Any::class)).isSameAs(tag)
    assertThat(request.tag<Any>()).isSameAs(tag)

fun <T : Any> Request.Builder.commonTag(
  type: KClass<T>,
  tag: T?,
) = apply {
  if (tag == null) {
    if (tags.isNotEmpty()) {
      (tags as MutableMap).remove(type)
    }
  } else {
    val mutableTags: MutableMap<KClass<*>, Any> =
      when {
        tags.isEmpty() -> mutableMapOf<KClass<*>, Any>().also { tags = it }
        else -> tags as MutableMap<KClass<*>, Any>
      }
    mutableTags[type] = tag

     */
    fun <T : Any> tag(
      type: KClass<T>,
      tag: T?,
    ): Builder = commonTag(type, type.cast(tag))

    /** Attaches [tag] to the request using `Object.class` as a key. */
    open fun tag(tag: Any?): Builder = commonTag(Any::class, tag)

    /**
     * Attaches [tag] to the request using [type] as a key. Tags can be read from a

		{ // Filter with And, Prefix & multiple Tag tags
			inputXML: ` <Filter>
							<And>
							<Prefix>key-prefix</Prefix>
							<Tag>
								<Key>key1</Key>
								<Value>value1</Value>
							</Tag>
							<Tag>
								<Key>key2</Key>
								<Value>value2</Value>
							</Tag>
							</And>
						</Filter>`,
			expectedErr: nil,
		},
		{ // Filter with And and multiple Tag tags
			inputXML: ` <Filter>
							<And>

    - **name**: each item must have a name
    - **description**: a long description
    - **price**: required
    - **tax**: if the item doesn't have tax, you can omit this
    - **tags**: a set of unique tag strings for this item
    """

   *
   * You may also specify a tag class like [DerHeader.TAG_CLASS_APPLICATION]. The default tag class
   * is [DerHeader.TAG_CLASS_CONTEXT_SPECIFIC].
   *
   * ```
   * Point ::= SEQUENCE {
   *   x [APPLICATION 0] INTEGER OPTIONAL,
   *   y [APPLICATION 1] INTEGER OPTIONAL
   * }
   * ```
   */
  fun withTag(
    tagClass: Int = DerHeader.TAG_CLASS_CONTEXT_SPECIFIC,
    tag: Long,