[AccessHeadersJava]: https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/AccessHeaders.java
 [AccessHeadersKotlin]: https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/kt/AccessHeaders.kt

    val request =
      Request
        .Builder()
        .url("https://square.com")
        .tag("a")
        .tag(null)
        .build()
    assertThat(request.tag()).isNull()
  }

  @Test
  fun removeAbsentTag() {
    val request =
      Request
        .Builder()
        .url("https://square.com")
        .tag(null)
        .build()
    assertThat(request.tag()).isNull()
  }

/*
 * Copyright (C) 2014 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

As the type, put the `List` that you imported from `typing`.

As the list is a type that contains some internal types, you put them in square brackets:

```Python hl_lines="4"
{!> ../../docs_src/python_types/tutorial006.py!}
```

////

/// info

Those internal types in the square brackets are called "type parameters".

In this case, `str` is the type parameter passed to `List` (or `list` in Python 3.9 and above).

/*
 * Copyright (C) 2018 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright (C) 2018 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

    super.onCreate(savedInstanceState)

    val client = OkHttpClient()

    // Ensure we are compiling against the right variant
    println(AndroidPlatform.isSupported)

    val url = "https://github.com/square/okhttp".toHttpUrl()
    println(url.topPrivateDomain())

    client.newCall(Request(url)).enqueue(
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,

/*
 * Copyright (C) 2018 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright (C) 2018 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,