changed GetDevices to GetDevice

there was no need to get the full device list. but for the cli there is
a need to access specific devices from the pnd via their uuid

nucleus/principalNetworkDomain.go

@@ -17,7 +17,7 @@ type PrincipalNetworkDomain interface {
 	RequestAll(string) error
 	GetName() string
 	GetDescription() string
-	GetDevices() map[uuid.UUID]*Device
+	GetDevice(uuid.UUID) (*Device, bool)
 	GetSBIs() map[string]SouthboundInterface
 }
 
@@ -45,8 +45,8 @@ func (pnd *pndImplementation) GetName() string {
 	return pnd.name
 }
 
-func (pnd *pndImplementation) GetDevices() map[uuid.UUID]*Device {
-	return pnd.devices
+func (pnd *pndImplementation) GetDevice(uuid uuid.UUID) (*Device, bool) {
+	return pnd.getDevice(uuid)
 }
 
 func (pnd *pndImplementation) GetDescription() string {
@@ -104,6 +104,11 @@ func (pnd *pndImplementation) removeDevice(uuid uuid.UUID) error {
 	return nil
 }
 
+func (pnd *pndImplementation) getDevice(uuid uuid.UUID) (*Device, bool) {
+	device, exists := pnd.devices[uuid]
+	return device, exists
+}
+
 func (pnd *pndImplementation) Request(uuid uuid.UUID, path string) error {
 	d := pnd.devices[uuid]
 	ctx := context.Background()

nucleus/southbound.go

@@ -62,6 +62,9 @@ func (oc *OpenConfig) SetNode() func(schema *yang.Entry, root interface{}, path
 	}
 }
 
+// deprecated
+// Use for prototyping only.
+// Use OpenConfig instead
 type AristaOC struct {
 	// deprecated
 	transport Transport