:term:`abstract base class` to help create those methods from a base set of
:meth:`~object.__getitem__`, :meth:`~object.__setitem__`,
:meth:`~object.__delitem__`, and :meth:`!keys`.
-Mutable sequences should provide methods :meth:`~sequence.append`,
-:meth:`~sequence.count`, :meth:`~sequence.index`, :meth:`~sequence.extend`,
-:meth:`~sequence.insert`, :meth:`~sequence.pop`, :meth:`~sequence.remove`,
-:meth:`~sequence.reverse` and :meth:`!sort`,
+
+Mutable sequences should provide methods
+:meth:`~sequence.append`, :meth:`~sequence.clear`, :meth:`~sequence.count`,
+:meth:`~sequence.extend`, :meth:`~sequence.index`, :meth:`~sequence.insert`,
+:meth:`~sequence.pop`, :meth:`~sequence.remove`, and :meth:`~sequence.reverse`,
like Python standard :class:`list` objects.
Finally, sequence types should implement addition (meaning concatenation) and
multiplication (meaning repetition) by defining the methods
:meth:`~object.__add__`, :meth:`~object.__radd__`, :meth:`~object.__iadd__`,
:meth:`~object.__mul__`, :meth:`~object.__rmul__` and :meth:`~object.__imul__`
described below; they should not define other numerical
-operators. It is recommended that both mappings and sequences implement the
+operators.
+
+It is recommended that both mappings and sequences implement the
:meth:`~object.__contains__` method to allow efficient use of the ``in``
operator; for
mappings, ``in`` should search the mapping's keys; for sequences, it should