feat: document set_lag_members on SwitchDriver

Adds the abstract set_lag_members() method (with docstring) implemented
by the ProCurve, NetGear and TP-Link Jetstream drivers for managing
LAG/trunk port membership.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

napalm_device_types/switch.py

@@ -10,7 +10,7 @@ Usage::
             ...
 """
 
-from typing import Dict
+from typing import Dict, List
 from napalm.base import NetworkDriver
 from napalm_device_types.models import (
     Dot1XPortDict,
@@ -375,6 +375,27 @@ class SwitchDriver(NetworkDriver):
         """
         raise NotImplementedError
 
+    def set_lag_members(self, lag_name: str, members: List[str]) -> None:
+        """
+        Sets the full member-port list of a LAG/trunk interface.
+
+        Diffs *members* against the LAG's current members (as reported by
+        ``get_interfaces()``'s ``lag_members`` field) and adds/removes ports
+        on the device to match. The LAG itself must already exist on the
+        device; this method only manages its membership.
+
+        :param lag_name: Name of the LAG/trunk interface as returned by
+            ``get_interfaces()`` (e.g. ``"Trk1"``, ``"ch1"``, ``"Lag1"``).
+        :param members: Full desired list of member port names.
+        :raises NotImplementedError: If the driver does not implement this method.
+        :raises ValueError: If *lag_name* does not refer to a valid LAG.
+
+        Example::
+
+            driver.set_lag_members("Lag1", ["GigabitEthernet0/1", "GigabitEthernet0/2"])
+        """
+        raise NotImplementedError
+
     def set_poe_enabled(self, interface: str, enabled: bool) -> None:
         """
         Administratively enables or disables PoE on a single port.