Check if in enable mode. Return boolean.

        :param check_string: Identification of privilege mode from device
        :type check_string: str

def check_enable_mode(self, check_string=""):
        """Check if in enable mode. Return boolean.

        :param check_string: Identification of privilege mode from device
        :type check_string: str
        """
        self.write_channel(self.RETURN)
        output = self.read_until_prompt()
        return check_string in output