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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 with_rank(self, rank):
 """Returns a shape based on `self` with the given rank. This method promotes a completely unknown shape to one with a known rank. Args: rank: An integer. Returns: A shape that is at least as specific as `self` with the given rank. Raises: ValueError: If `self` does not represent a shape with the given `rank`. """

        try:
            return self.merge_with(unknown_shape(ndims=rank))
        except ValueError:
            raise ValueError("Shape %s must have rank %d" % (self, rank))