Set scalar value into the array.

        Parameters
        ----------
        indexer : any
            The indexer to set the value at.
        value : str
            The value to assign at the given locations.

        Raises
        ------
        ValueError
            Raised when ``value`` is not a value element of this this label
            array.

def set_scalar(self, indexer, value):
        """
        Set scalar value into the array.

        Parameters
        ----------
        indexer : any
            The indexer to set the value at.
        value : str
            The value to assign at the given locations.

        Raises
        ------
        ValueError
            Raised when ``value`` is not a value element of this this label
            array.
        """
        try:
            value_code = self.reverse_categories[value]
        except KeyError:
            raise ValueError("%r is not in LabelArray categories." % value)

        self.as_int_array()[indexer] = value_code