def tagmask(self, tags):
        """
        :returns: a boolean array with True where the assets has tags
        """
        mask = numpy.zeros(len(tags), bool)
        for t, tag in enumerate(tags):
            tagname, tagvalue = tag.split('=')
            mask[t] = self.tagvalue(tagname) == tagvalue
        return mask
:returns: a boolean array with True where the assets has tags