Refactor nxos ntp for mypy typing

Making NTPPeerDict and NTPServerDict non-identical caused
issues with typing since we wre unable to assert the type of the
return dictionary easily.  This refactor allows us to explicitly
state the return type for each function.

Author: bewing

napalm/base/models.py

@@ -223,17 +223,7 @@
 
 NTPPeerDict = TypedDict(
     "NTPPeerDict",
-    {
-        "address": str,
-        "port": int,
-        "version": int,
-        "association_type": str,
-        "iburst": bool,
-        "prefer": bool,
-        "network_instance": str,
-        "source_address": str,
-        "key_id": int,
-    },
+    {},
     total=False,
 )
 

napalm/nxos/nxos.py

@@ -1204,27 +1204,32 @@ def get_arp_table(self, vrf: str = "") -> List[models.ARPTableDict]:
             )
         return arp_table
 
-    def _get_ntp_entity(
-        self, peer_type: str
-    ) -> Dict[str, Union[models.NTPPeerDict, models.NTPServerDict]]:
-        ntp_entities: Dict[str, Union[models.NTPPeerDict, models.NTPServerDict]] = {}
+    def _filter_ntp_table(self, peer_type: str) -> List[str]:
+        ret = []
         command = "show ntp peers"
         ntp_peers_table = self._get_command_table(command, "TABLE_peers", "ROW_peers")
-
         for ntp_peer in ntp_peers_table:
             if ntp_peer.get("serv_peer", "").strip() != peer_type:
                 continue
             peer_addr = napalm.base.helpers.ip(ntp_peer.get("PeerIPAddress").strip())
-            # Ignore the type of the following line until NTP data is modelled
-            ntp_entities[peer_addr] = {}  # type: ignore
-
-        return ntp_entities
+            ret.append(peer_addr)
+        return ret
 
     def get_ntp_peers(self) -> Dict[str, models.NTPPeerDict]:
-        return self._get_ntp_entity("Peer")
+        ntp_entities: Dict[str, models.NTPPeerDict] = {}
+        peers = self._filter_ntp_table("Peer")
+        for peer_addr in peers:
+            ntp_entities[peer_addr] = {}
+
+        return ntp_entities
 
     def get_ntp_servers(self) -> Dict[str, models.NTPServerDict]:
-        return self._get_ntp_entity("Server")
+        ntp_entities: Dict[str, models.NTPServerDict] = {}
+        peers = self._filter_ntp_table("Server")
+        for peer_addr in peers:
+            ntp_entities[peer_addr] = {}
+
+        return ntp_entities
 
     def get_ntp_stats(self) -> List[models.NTPStats]:
         ntp_stats: List[models.NTPStats] = []