Returns ``True`` if a connection between the given objects exists,
        else ``False``.

def connection_exists(self, from_obj, to_obj):
        """
        Returns ``True`` if a connection between the given objects exists,
        else ``False``.
        """
        self._validate_ctypes(from_obj, to_obj)
        return self.connections.filter(from_pk=from_obj.pk, to_pk=to_obj.pk).exists()