Each instance of the `SessionLocal` class will be a database session. The class itself is not a database session yet.

But once we create an instance of the `SessionLocal` class, this instance will be the actual database session.

We name it `SessionLocal` to distinguish it from the `Session` we are importing from SQLAlchemy.

We will use `Session` (the one imported from SQLAlchemy) later.

   * @return a long of a concatenated 8 bytes
   */
  static long load64Safely(byte[] input, int offset, int length) {
    long result = 0;
    // Due to the way we shift, we can stop iterating once we've run out of data, the rest
    // of the result already being filled with zeros.

    // This loop is critical to performance, so please check HashBenchmark if altering it.
    int limit = Math.min(length, 8);

same. We’ve chosen Kotlin because it gives us powerful new capabilities while integrating closely
with Java.

We spent a lot of time and energy on retaining strict compatibility with OkHttp 3.x. We’re even
keeping the package name the same: `okhttp3`!

There are three kinds of compatibility we’re tracking:

    could use new flow control capacity before acknowledging it, causing strict HTTP/2 servers to
    fail the call.


## Version 4.1.1

_2019-09-05_

 *  Fix: Don't drop repeated headers when validating cached responses. In our Kotlin upgrade we
    introduced a regression where we iterated the number of unique header names rather than then

1. If the destination has a waypoint proxy, we must send to it to the waypoint (using HBONE).
   When we do this, we will want to preserve the original destination Service IP, as the waypoint can do a better job picking a backend pod than we can.

 * com.google.common.base.FinalizableReference}.
 *
 * <p>While this class is public, we consider it to be *internal* and not part of our published API.
 * It is public so we can access it reflectively across class loaders in secure environments.
 *
 * <p>This class can't depend on other Guava code. If we were to load this class in the same class

In OkHttp we expose a blocking API over a framed protocol. This document explains the code and policy that makes that work.

### Threads

#### Application's calling thread

        }
        return toReturn;
      }

      @GuardedBy("lock")
      /*
       * The GuardedBy checker warns us that we're not holding cancellationDelegate.lock. But in
       * fact we are holding it because it is the same as this.lock, which we know we are holding,
       * thanks to @GuardedBy above. (cancellationDelegate.lock is initialized to this.lock in the
       * call to `new SupplantableFuture` below.)

 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AbstractFuture} (and all of {@code
 * com.google.common.util.concurrent}) in degenerate class loaders which make certain platform
 * classes unavailable. Then we construct a test suite so we can run the normal AbstractFutureTest
 * test methods in these degenerate classloaders.
 */

    // DISCUSS
    "EqualsGetClass", // Let's agree if we want to adopt Error Prone's idea of valid equals()
    "JdkObsolete", // Most of the checks are good, but we do not want to replace all LinkedLists without a good reason

    // NEVER
    "MissingSummary", // We have another mechanism to check Javadocs on public API
    "InjectOnConstructorOfAbstractClass", // We use abstract injection as a pattern