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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 from_obj(cls, cls_obj):
 """Parse the generateDS object and return an Entity instance. This will attempt to extract type information from the input object and pass it to entity_class to resolve the correct class for the type. Args: cls_obj: A generateDS object. Returns: An Entity instance. """

        if not cls_obj:
            return None

        typekey = cls.objkey(cls_obj)
        klass   = cls.entity_class(typekey)
        return klass.from_obj(cls_obj)