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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 start(cls, ev):
 """ Event handler which starts the request to REST API. """

        # somehow the first call doesn't stop the propagation
        ev.stopPropagation()
        ev.preventDefault()

        # make sure, that `author` was filled
        author = cls.input_el.value.strip()
        if not author:
            cls.input_el.style.border = "2px solid red"
            return

        cls.hide_errors()

        AuthorBar.show(50)
        make_request(
            url=join(settings.API_PATH, "aleph/authors_by_name"),
            data={"name": author},
            on_complete=cls.on_complete
        )