doc changes for 3d grouped convolutions

theano/gpuarray/dnn.py

@@ -1103,6 +1103,9 @@ def dnn_conv3d(img, kerns, border_mode='valid', subsample=(1, 1, 1), dilation=(1
         should be done. Possible values are 'as_input', 'float16', 'float32'
         and 'float64'. Default is the value of
         :attr:`config.dnn.conv.precision`.
+    num_groups :
+        Divides the image, kernel and output tensors into num_groups
+        separate groups. Each which carry out convolutions separately
 
 
     .. warning:: The cuDNN library only works with GPUs that have a compute