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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 reset_placeholder_dropdown(cls, input_el):
 """ Reset the element back to default. """

        text = cls.get_placeholder_text(input_el)
        cls.set_placeholder_text(
            input_el=input_el,
            text=text.replace(cls._dropdown_text, "")
        )