*/
    abstract @Nullable N visitNext(Deque<Iterator<? extends N>> horizon);
  }

  /** Poor man's method reference for {@code Deque::addFirst} and {@code Deque::addLast}. */
  private enum InsertionOrder {
    FRONT {
      @Override
      <T> void insertInto(Deque<T> deque, T value) {
        deque.addFirst(value);
      }
    },
    BACK {
      @Override

import dataclasses
import datetime
from collections import defaultdict, deque
from collections.abc import Callable
from decimal import Decimal
from enum import Enum
from ipaddress import (
    IPv4Address,
    IPv4Interface,
    IPv4Network,
    IPv6Address,
    IPv6Interface,
    IPv6Network,
)
from pathlib import Path, PurePath
from re import Pattern
from types import GeneratorType
from typing import Annotated, Any

import com.google.common.collect.Iterators;
import com.google.common.collect.Maps;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Deque;
import java.util.Iterator;
import java.util.Map;
import java.util.Objects;
import java.util.Queue;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**

    // Starting with an 8k buffer, double the size of each successive buffer. Smaller buffers
    // quadruple in size until they reach 8k, to minimize the number of small reads for longer
    // streams. Buffers are retained in a deque so that there's no copying between buffers while
    // reading and so all of the bytes in each new allocated buffer are available for reading from
    // the stream.
    for (int bufSize = initialBufferSize;

import java.nio.ShortBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collection;
import java.util.Comparator;
import java.util.Currency;
import java.util.Deque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Locale;
import java.util.Map;

import java.nio.ShortBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collection;
import java.util.Comparator;
import java.util.Currency;
import java.util.Deque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Locale;
import java.util.Map;

* ✨ Add support for `deque` objects and children in `jsonable_encoder`. PR [#9433](https://github.com/tiangolo/fastapi/pull/9433) by [@cranium](https://github.com/cranium).

### Docs