update signatures of choose()

theano/tensor/var.py

@@ -762,13 +762,13 @@ class _tensor_py_operators(object):
         """Fill inputted tensor with the assigned value."""
         return theano.tensor.basic.fill(self, value)
 
-    def choose(self, a, choices, out=None, mode='raise'):
+    def choose(self, choices, out=None, mode='raise'):
         """
         Construct an array from an index array and a set of arrays to choose
         from.
 
         """
-        return theano.tensor.basic.choose(a, choices, out=None, mode='raise')
+        return theano.tensor.basic.choose(self, choices, out=None, mode='raise')
 
     def squeeze(self):
         """