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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 set_variations(self, variations):
 """Sets the OpenType font variations for the font options object. Font variations are specified as a string with a format that is similar to the CSS font-variation-settings. The string contains a comma-separated list of axis assignments, which each assignment consists of a 4-character axis name and a value, separated by whitespace and optional equals sign. :param variations: the new font variations, or ``None``. *New in cairo 1.16.* *New in cairocffi 0.9.* """

        if variations is None:
            variations = ffi.NULL
        else:
            variations = _encode_string(variations)
        cairo.cairo_font_options_set_variations(self._pointer, variations)
        self._check_status()