Prepare the given value to be stored in the index

        It first calls ``transform_value`` if ``transform`` is ``True``, then
        calls the ``from_python`` method of the field, then cast the result
        to a str.

        Parameters
        ----------
        value: any
            The value to normalize
        transform: bool
            If ``True`` (the default), the value will be passed to ``transform_value``.
            The returned value will then be used.

        Returns
        -------
        str
            The value, normalized

def normalize_value(self, value, transform=True):
        """Prepare the given value to be stored in the index

        It first calls ``transform_value`` if ``transform`` is ``True``, then
        calls the ``from_python`` method of the field, then cast the result
        to a str.

        Parameters
        ----------
        value: any
            The value to normalize
        transform: bool
            If ``True`` (the default), the value will be passed to ``transform_value``.
            The returned value will then be used.

        Returns
        -------
        str
            The value, normalized

        """
        if transform:
            value = self.transform_value(value)
        return str(self.field.from_python(value))