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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def encode(obj, sedes=None, infer_serializer=True, cache=True):
 """Encode a Python object in RLP format. By default, the object is serialized in a suitable way first (using :func:`rlp.infer_sedes`) and then encoded. Serialization can be explicitly suppressed by setting `infer_serializer` to ``False`` and not passing an alternative as `sedes`. If `obj` has an attribute :attr:`_cached_rlp` (as, notably, :class:`rlp.Serializable`) and its value is not `None`, this value is returned bypassing serialization and encoding, unless `sedes` is given (as the cache is assumed to refer to the standard serialization which can be replaced by specifying `sedes`). If `obj` is a :class:`rlp.Serializable` and `cache` is true, the result of the encoding will be stored in :attr:`_cached_rlp` if it is empty. :param sedes: an object implementing a function ``serialize(obj)`` which will be used to serialize ``obj`` before encoding, or ``None`` to use the infered one (if any) :param infer_serializer: if ``True`` an appropriate serializer will be selected using :func:`rlp.infer_sedes` to serialize `obj` before encoding :param cache: cache the return value in `obj._cached_rlp` if possible (default `True`) :returns: the RLP encoded item :raises: :exc:`rlp.EncodingError` in the rather unlikely case that the item is too big to encode (will not happen) :raises: :exc:`rlp.SerializationError` if the serialization fails """

    if isinstance(obj, Serializable):
        cached_rlp = obj._cached_rlp
        if sedes is None and cached_rlp:
            return cached_rlp
        else:
            really_cache = (
                cache and
                sedes is None
            )
    else:
        really_cache = False

    if sedes:
        item = sedes.serialize(obj)
    elif infer_serializer:
        item = infer_sedes(obj).serialize(obj)
    else:
        item = obj

    result = encode_raw(item)
    if really_cache:
        obj._cached_rlp = result
    return result