Set the value of form element by its number in the form

        :param number: number of element
        :param value: value which should be set to element

def set_input_by_number(self, number, value):
        """
        Set the value of form element by its number in the form

        :param number: number of element
        :param value: value which should be set to element
        """

        sel = XpathSelector(self.form)
        elem = sel.select('.//input[@type="text"]')[number].node()
        return self.set_input(elem.get('name'), value)