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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 get_symbol_map(self):
 """ If you need the symbol map, use this method. The symbol map is an array of string pairs mapping common tokens to X Keysym strings, such as "alt" to "Alt_L" :return: array of strings. """

        # todo: make sure we return a list of strings!
        sm = _libxdo.xdo_get_symbol_map()

        # Return value is like:
        # ['alt', 'Alt_L', ..., None, None, None, ...]
        # We want to return only values up to the first None.
        # todo: any better solution than this?
        i = 0
        ret = []
        while True:
            c = sm[i]
            if c is None:
                return ret
            ret.append(c)
            i += 1