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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 aliased_as(self, name):
 """ Create an alias of this stream. Returns an alias of this stream with name `name`. When invocation of an SPL operator requires an :py:class:`~streamsx.spl.op.Expression` against an input port this can be used to ensure expression matches the input port alias regardless of the name of the actual stream. Example use where the filter expression for a ``Filter`` SPL operator uses ``IN`` to access input tuple attribute ``seq``:: s = s.aliased_as('IN') params = {'filter': op.Expression.expression('IN.seq % 4ul == 0ul')} f = op.Map('spl.relational::Filter', stream, params = params) Args: name(str):
 Name for returned stream. Returns: Stream: Alias of this stream with ``name`` equal to `name`. .. versionadded:: 1.9 """

        stream = copy.copy(self)
        stream._alias = name
        return stream