Return a single Node by (form,valu) tuple.

        Args:
            ndef ((str,obj)): A (form,valu) ndef tuple.  valu must be
            normalized.

        Returns:
            (synapse.lib.node.Node): The Node or None.

async def getNodeByNdef(self, ndef):
        '''
        Return a single Node by (form,valu) tuple.

        Args:
            ndef ((str,obj)): A (form,valu) ndef tuple.  valu must be
            normalized.

        Returns:
            (synapse.lib.node.Node): The Node or None.
        '''
        buid = s_common.buid(ndef)
        return await self.getNodeByBuid(buid)