optimize imports

tests/python/unittest/test_viz.py

@@ -15,9 +15,11 @@
 # specific language governing permissions and limitations
 # under the License.
 
-import mxnet as mx
-import warnings
 import unittest
+import warnings
+
+import mxnet as mx
+
 
 def test_print_summary():
     data = mx.sym.Variable('data')
@@ -56,7 +58,7 @@ def test_plot_network():
     assert len(w) == 1
     assert "There are multiple variables with the same name in your graph" in str(w[-1].message)
     assert "fc" in str(w[-1].message)
-    
+
 if __name__ == "__main__":
     import nose
     nose.runmodule()