Face landmarks (fpenet)

Hi! i am using the model Fpenet to get face landmarks in deepstream, but i dont know how get the landmarks, im using this line:
landmarks = buffer_as_nparray(layer.buffer,(80,))
this return negative values and only a list with 80 values ,

in the nvidia documentation it tells me that you can get an output of (N,2) where you get the coordinates of
the landmarks, I would like to know how or what command I should use to obtain those landmarks