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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 by_lookup(self, style_key, style_value):
 """Return a processor that extracts the style from `mapping`. Parameters style_key : str A style key. style_value : dict A dictionary with a "lookup" key whose value is a "mapping" style value that maps a field value to either a style attribute (str) and a boolean flag indicating to use the style attribute named by `style_key`. Returns ------- A function. """

        style_attr = style_key if self.style_types[style_key] is bool else None
        mapping = style_value["lookup"]

        def proc(value, result):
            try:
                lookup_value = mapping[value]
            except (KeyError, TypeError):
                # ^ TypeError is included in case the user passes non-hashable
                # values.
                return result

            if not lookup_value:
                return result
            return self.render(style_attr or lookup_value, result)
        return proc