[Hotfix] Fix unsupervised graphsage (#2143)

* hotfix

* Hotfix
Co-authored-by: Ubuntu <ubuntu@ip-172-31-87-240.ec2.internal>

examples/pytorch/graphsage/train_sampling_unsupervised.py

@@ -34,7 +34,7 @@ class NegativeSampler(object):
             dst = self.weights.multinomial(n, replacement=True)
             dst = dst.view(-1, 1, self.k).expand(-1, self.k, -1).flatten()
         else:
-            dst = self.weights.multinomial(n, replacement=True)
+            dst = self.weights.multinomial(n*self.k, replacement=True)
         src = src.repeat_interleave(self.k)
         return src, dst