Remove documentation that appears to promote unsupported direct guards usage (#314)

Author: dataflake

CHANGES.rst

@@ -4,6 +4,8 @@ Changes
 8.2 (unreleased)
 ----------------
 
+- Remove documentation that appears to promote unsupported direct guards usage.
+
 - Move package metadata from setup.py to pyproject.toml.
 
 - Drop support for Python 3.9.

docs/usage/policy.rst

@@ -167,71 +167,3 @@ unsafe operations, such as opening files:
     Traceback (most recent call last):
       ...
     NameError: name 'open' is not defined
-
-Guards
-......
-
-Here's an example of a write guard that never lets restricted code
-modify (assign, delete an attribute or item) except dictionaries and
-lists:
-
-.. code-block:: pycon
-
-    >>> from RestrictedPython.Guards import full_write_guard
-    >>> _write_ = full_write_guard
-    >>> _getattr_ = getattr
-
-    >>> class BikeShed(object):
-    ...     colour = 'green'
-    ...
-    >>> shed = BikeShed()
-
-Normally accessing attributes works as expected, because we're using
-the standard ``getattr`` function for the ``_getattr_`` guard:
-
-.. code-block:: pycon
-
-    >>> src = '''
-    ... print(shed.colour)
-    ... result = printed
-    ... '''
-    >>> code = compile_restricted(src, '<string>', 'exec')
-    >>> exec(code)
-
-    >>> result
-    'green\n'
-
-However, changing an attribute doesn't work:
-
-.. code-block:: pycon
-
-    >>> src = '''
-    ... shed.colour = 'red'
-    ... '''
-    >>> code = compile_restricted(src, '<string>', 'exec')
-    >>> exec(code)
-    Traceback (most recent call last):
-      ...
-    TypeError: attribute-less object (assign or del)
-
-As said, this particular write guard (``full_write_guard``) will allow
-restricted code to modify lists and dictionaries:
-
-.. code-block:: pycon
-
-    >>> fibonacci = [1, 1, 2, 3, 4]
-    >>> transl = dict(one=1, two=2, tres=3)
-    >>> src = '''
-    ... # correct mistake in list
-    ... fibonacci[-1] = 5
-    ... # one item doesn't belong
-    ... del transl['tres']
-    ... '''
-    >>> code = compile_restricted(src, '<string>', 'exec')
-    >>> exec(code)
-
-    >>> fibonacci
-    [1, 1, 2, 3, 5]
-
-    >>> sorted(transl.keys())
-    ['one', 'two']