def get_tags(self, field):
        """Get the set of tags for a given field.

        .. note::
            The named field must be accessible given the current set of values
            defined.

        Parameters
        ----------
        field : str
            The field whose tag should be read.

        Returns
        -------
        set([tag, ...])

        Raises
        ------
        UnavailableFieldError
            If the field does not exist or is not available.
        """
        return self.fields.get_field(field, self.field_values).tags.copy()