Removing notes about @override decorator from advanced usage docs

docs/advanced_usage.rst

@@ -36,90 +36,3 @@ that will be called to provide injectable value.
 
     example_callback()
     example_callback()
-
-Overriding catalogs
--------------------
-
-Any catalog can be overridden by another catalog.
-
-Example:
-
-.. code-block:: python
-
-    """Catalog overriding example."""
-
-    import sqlite3
-
-    from objects.catalog import AbstractCatalog
-    from objects.catalog import override
-
-    from objects.providers import Singleton
-    from objects.providers import NewInstance
-
-    from objects.injections import KwArg
-    from objects.injections import Attribute
-
-
-    class ObjectA(object):
-
-        """ObjectA has dependency on database."""
-
-        def __init__(self, database):
-            """Initializer.
-
-            Database dependency need to be injected via init arg."""
-            self.database = database
-
-        def get_one(self):
-            """Select one from database and return it."""
-            return self.database.execute('SELECT 1')
-
-
-    class ObjectAMock(ObjectA):
-
-        """Mock of ObjectA.
-
-        Has no dependency on database.
-        """
-
-        def __init__(self):
-            """Initializer."""
-
-        def get_one(self):
-            """Select one from database and return it.
-
-            Mock makes no database queries and always returns two instead of one.
-            """
-            return 2
-
-
-    class Catalog(AbstractCatalog):
-
-        """Catalog of objects providers."""
-
-        database = Singleton(sqlite3.Connection,
-                             KwArg('database', ':memory:'),
-                             KwArg('timeout', 30),
-                             KwArg('detect_types', True),
-                             KwArg('isolation_level', 'EXCLUSIVE'),
-                             Attribute('row_factory', sqlite3.Row))
-
-        object_a = NewInstance(ObjectA,
-                               KwArg('database', database))
-
-
-    @override(Catalog)
-    class SandboxCatalog(Catalog):
-
-        """Sandbox objects catalog with some mocks that overrides Catalog."""
-
-        object_a = NewInstance(ObjectAMock)
-
-
-    # Creating several `ObjectA` instances.
-    object_a_1 = Catalog.object_a()
-    object_a_2 = Catalog.object_a()
-
-    # Making some asserts.
-    assert object_a_1 is not object_a_2
-    assert object_a_1.get_one() == object_a_2.get_one() == 2