## Context Managers

### What are "Context Managers"

"Context Managers" are any of those Python objects that you can use in a `with` statement.

 * methods for more details.
 *
 * <p>Note that this implementation is not synchronized. If multiple threads access the same cell of
 * an {@code ArrayTable} concurrently and one of the threads modifies its value, there is no
 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}

   * that use {@code comparator} to determine the least and greatest elements.
   */
  /*
   * TODO(cpovirk): Change to Comparator<? super B> to permit Comparator<@Nullable ...> and
   * Comparator<SupertypeOfB>? What we have here matches the immutable collections, but those also
   * expose a public Builder constructor that accepts "? super." So maybe we should do *that*
   * instead.
   */

 * take advantage of the {@linkplain Futures utilities built atop the class}. The way that you will
 * create {@code ListenableFuture} instances depends on how you currently create {@code Future}
 * instances:
 *
 * <ul>
 *   <li>If you receive them from an {@code java.util.concurrent.ExecutorService}, convert that

 * take advantage of the {@linkplain Futures utilities built atop the class}. The way that you will
 * create {@code ListenableFuture} instances depends on how you currently create {@code Future}
 * instances:
 *
 * <ul>
 *   <li>If you receive them from an {@code java.util.concurrent.ExecutorService}, convert that

}

// PolicyRule holds information that describes a policy rule, but does not contain information
// about who the rule applies to or which namespace the rule applies to.
message PolicyRule {
  // Verbs is a list of Verbs that apply to ALL the ResourceKinds contained in this rule. '*' represents all verbs.
  repeated string verbs = 1;

 *  * **Canceled:** the web socket connection failed. Messages that were successfully enqueued by
 *    either peer may not have been transmitted to the other.
 *
 * Note that the state progression is independent for each peer. Arriving at a gracefully-closed
 * state indicates that a peer has sent all of its outgoing messages and received all of its
 * incoming messages. But it does not guarantee that the other peer will successfully receive all of

### Locks

We have 3 different things that we synchronize on.

#### Http2Connection

   * protect ourselves from that we want to make sure that tasks don't spin too much waiting for the
   * interrupting thread to complete the protocol.
   */
  /*
   * This test hangs (or maybe is just *very* slow) under Android.
   *
   * TODO(b/218700094): Ideally, get this to pass under Android. Failing that, convince ourselves

`Body` also returns objects of a subclass of `FieldInfo` directly. And there are others you will see later that are subclasses of the `Body` class.

Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

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