Add example for str.encode()

WIP to fix python#106318

Author: blaisep

Doc/library/stdtypes.rst

@@ -1817,9 +1817,15 @@ expression support in the :mod:`re` module).
    See :ref:`error-handlers` for details.
 
    For performance reasons, the value of *errors* is not checked for validity
-   unless an encoding error actually occurs,
-   :ref:`devmode` is enabled
-   or a :ref:`debug build <debug-build>` is used.
+   unless an encoding error actually occurs, :ref:`devmode` is enabled or a :ref:`debug build <debug-build>` is used.
+   For example::
+
+      >>> encoded_str_to_byte = 'Python'.encode()
+      >>> type(encoded_str_to_byte)
+      <class 'bytes'>
+      >>> encoded_str_to_byte
+      b'Python'
+
 
    .. versionchanged:: 3.1
       Added support for keyword arguments.