Transform string value to an actual data type of the same value.

def _typed_value(self, value):
        """ Transform string value to an actual data type of the same value. """

        if value not in self._value_cache:
            new_value = value
            if is_int(value):
                new_value = int(value)
            elif is_float(value):
                new_value = float(value)
            elif is_bool(value):
                new_value = to_bool(value)
            elif is_none(value):
                new_value = None
            self._value_cache[value] = new_value

        return self._value_cache[value]