### O que são gerenciadores de contexto

"Gerenciadores de Contexto" são qualquer um dos objetos Python que podem ser utilizados com a declaração `with`.

Por exemplo, <a href="https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files" class="external-link" target="_blank">você pode utilizar `with` para ler um arquivo</a>:

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		case "PartNumber":
			z.PartNumber, err = dc.ReadInt()
			if err != nil {
				err = msgp.WrapError(err, "PartNumber")
				return
			}
		case "Algorithm":
			{
				var zb0002 uint
				zb0002, err = dc.ReadUint()
				if err != nil {
					err = msgp.WrapError(err, "Algorithm")
					return
				}
				z.Algorithm = BitrotAlgorithm(zb0002)

		// Buffer size greater than object size. - 6
		{
			volume, "myobject", 0, 16,
			[]byte("hello, world"),
			io.ErrUnexpectedEOF,
		},
		// Reading from an offset success. - 7
		{
			volume, "myobject", 7, 5,
			[]byte("world"), nil,
		},
		// Reading from an object but buffer size greater. - 8
		{
			volume, "myobject",
			7, 8,
			[]byte("world"),
			io.ErrUnexpectedEOF,
		},

    }
  }

  private void doTestExistsThrowsSecurityException() throws IOException, URISyntaxException {
    File file = null;
    // In Java 9, Logger may read the TZ database. Only disallow reading the class path URLs.
    final PermissionCollection readClassPathFiles =
        new FilePermission("", "read").newPermissionCollection();
    for (URL url : ClassPath.parseJavaClassPath()) {

  }

  @J2ktIncompatible // serialization
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    ConcurrentMap<E, Integer> deserializedCountMap =
        (ConcurrentMap<E, Integer>) requireNonNull(stream.readObject());

* `Field(index=True)` tells SQLModel that it should create a **SQL index** for this column, that would allow faster lookups in the database when reading data filtered by this column.

    SQLModel will know that something declared as `str` will be a SQL column of type `TEXT` (or `VARCHAR`, depending on the database).

### Create an Engine

   * the traverser cannot guarantee that it will not follow symbolic links to directories as it is
   * possible for a directory to be replaced with a symbolic link between checking if the file is a
   * directory and actually reading the contents of that directory.
   *
   * <p>If the {@link Path} passed to one of the traversal methods does not exist or is not a
   * directory, no exception will be thrown and the returned {@link Iterable} will contain a single

   * the traverser cannot guarantee that it will not follow symbolic links to directories as it is
   * possible for a directory to be replaced with a symbolic link between checking if the file is a
   * directory and actually reading the contents of that directory.
   *
   * <p>If the {@link Path} passed to one of the traversal methods does not exist or is not a
   * directory, no exception will be thrown and the returned {@link Iterable} will contain a single

    val editor = cache.edit("k1")!!
    assertThat(cache["k1"]).isNull()
    editor.commit()
  }

  @ParameterizedTest
  @ArgumentsSource(FileSystemParamProvider::class)
  fun `Windows cannot write while reading`(parameters: Pair<FileSystem, Boolean>) {
    setUp(parameters.first, parameters.second)
    Assumptions.assumeTrue(windows)

    set("k1", "a", "a")
    val snapshot = cache["k1"]!!

   * body. This was misleading for tracing because it was too early.
   */
  open fun responseBodyStart(call: Call) {
  }

  /**
   * Invoked immediately after receiving a response body and completing reading it.
   *
   * Will only be invoked for requests having a response body e.g. won't be invoked for a web socket
   * upgrade.
   *