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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 import_lookup_class(lookup_class):
 """ Import lookup_class as a dotted base and ensure it extends LookupBase """

    from selectable.base import LookupBase
    if isinstance(lookup_class, string_types):
        mod_str, cls_str = lookup_class.rsplit('.', 1)
        mod = import_module(mod_str)
        lookup_class = getattr(mod, cls_str)
    if not issubclass(lookup_class, LookupBase):
        raise TypeError('lookup_class must extend from selectable.base.LookupBase')
    return lookup_class