[Paraview] TypeError: WriteImage() takes exactly 3 arguments (1 given)

[Anton Shterenlikht]

I get this error:

>>> view.WriteImage("z.png")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/paraview-3.10/site-packages/paraview/servermanager.py", line 331, in __ConvertArgumentsAndCall
    retVal = func(*newArgs)
TypeError: WriteImage() takes exactly 3 arguments (1 given)
>>> 

The tutorial suggests that just the filename is enough:

http://paraview.org/Wiki/ParaView/Python_Scripting

Anyway, I can see in other examples that the second argument
is the file format, e.g.:

view.WriteImage("z.png","vtkPNGWriter")

but this gives the same error:

>>> view.WriteImage("z.png","vtkPNGWriter")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/paraview-3.10/site-packages/paraview/servermanager.py", line 331, in __ConvertArgumentsAndCall
    retVal = func(*newArgs)
TypeError: WriteImage() takes exactly 3 arguments (2 given)
>>> 

I cannot find what the third argument must be.

Please help

Anton