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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_class_name(name, theme_element):
 """ Create an themeable by name Parameters name : str Class name theme_element : element object One of :class:`element_line`, :class:`element_rect`, :class:`element_text` or :class:`element_blank` Returns ------- out : Themeable """

        msg = "No such themeable element {}".format(name)
        try:
            klass = themeable._registry[name]
        except KeyError:
            raise PlotnineError(msg)

        if not issubclass(klass, themeable):
            raise PlotnineError(msg)

        return klass(theme_element)