operation does not return the correct type on TF_Input

[SergeStinckwich]

Sending operation message to TF_Input returns an ExternalData object instead of an instance of TF_Operation. See following example :

	| graph c1 c2 sum1 sum2 session result |
	graph := TF_Graph create.
	c1 := graph const: 'c1' value: 3.0 asTensor.
	c2 := graph const: 'c2' value: 4.0 asTensor.
	sum1 := c1 + c2.
	sum2 := sum1 + sum1.
	session := TF_Session on: graph.
	result := session runOutput: (sum2 output: 0).
	input := (graph operationNamed: 'Add_3') input:0.
	input operation