def get_span_kind_as_string(self, span):
        """
            Will retrieve the `span.kind` tag and return the appropriate string value for the Instana backend or
            None if the tag is set to something we don't recognize.

        :param span: The span to search for the `span.kind` tag
        :return: String
        """
        kind = None
        if "span.kind" in span.tags:
            if span.tags["span.kind"] in self.entry_kind:
                kind = "entry"
            elif span.tags["span.kind"] in self.exit_kind:
                kind = "exit"
            else:
                kind = "intermediate"
        return kind