fix plot bug: do not overwrite the path used for plot

The plot function failed to recognize 'path' as part
of the network due to the reuse of the 'path' variable.
This led to errors when attempting to plot.

Solution is to use a different name for the deepcopy of
path elements used to record the propagation results
'propagated_path'.

Signed-off-by: EstherLerouzic <esther.lerouzic@orange.com>
Change-Id: I0351c37de0d74391ebeb68e974b777b1f51572aa

gnpy/tools/cli_examples.py

@@ -225,14 +225,14 @@ def transmission_main_example(args=None):
           + '                       transceiver output power = '
           + f'{pretty_summary_print(per_label_average(watt2dbm(infos.tx_power), infos.label))}dBm,\n'
           + f'                       nb_channels = {infos.number_of_channels})')
-    for path, power_dbm in zip(propagations_for_path, powers_dbm):
+    for mypath, power_dbm in zip(propagations_for_path, powers_dbm):
         if power_mode:
             print(f'Input optical power reference in span = {ansi_escapes.cyan}{power_dbm:.2f} '
                   + f'dBm{ansi_escapes.reset}:')
         else:
             print('\nPropagating in {ansi_escapes.cyan}gain mode{ansi_escapes.reset}: power cannot be set manually')
         if len(powers_dbm) == 1:
-            for elem in path:
+            for elem in mypath:
                 print(elem)
             if power_mode:
                 print(f'\nTransmission result for input optical power reference in span = {power_dbm:.2f} dBm:')
@@ -240,7 +240,7 @@ def transmission_main_example(args=None):
                 print('\nTransmission results:')
             print(f'  Final GSNR (0.1 nm): {ansi_escapes.cyan}{mean(destination.snr_01nm):.02f} dB{ansi_escapes.reset}')
         else:
-            print(path[-1])
+            print(mypath[-1])
 
     if args.save_network is not None:
         save_network(network, args.save_network)