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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 select_to_constraint(cls, dataset, selection):
 """ Transform a selection dictionary to an iris Constraint. """

        import iris

        def get_slicer(start, end):
            def slicer(cell):
                return start <= cell.point < end
            return slicer
        constraint_kwargs = {}
        for dim, constraint in selection.items():
            if isinstance(constraint, slice):
                constraint = (constraint.start, constraint.stop)
            if isinstance(constraint, tuple):
                if constraint == (None, None):
                    continue
                constraint = get_slicer(*constraint)
            dim = dataset.get_dimension(dim, strict=True)
            constraint_kwargs[dim.name] = constraint
        return iris.Constraint(**constraint_kwargs)