Fixed name clash in plot.py

plot.py

@@ -1,4 +1,3 @@
-import constellation
 from constellation import util
 import torch
 from matplotlib import pyplot
@@ -23,9 +22,8 @@ fig = pyplot.figure()
 ax = SubplotZero(fig, 111)
 fig.add_subplot(ax)
 
-constellation = model.get_constellation()
 util.plot_constellation(
-    ax, constellation,
+    ax, model.get_constellation(),
     model.channel, model.decoder,
     grid_step=0.001, noise_samples=0
 )