You’re using the Functional API there, correct? The abstract syntax looks like this…
NOTE: code fragment edited to incorporate @paulinpaloalto 's response below which provided a more accurate nomenclature.
this_layer_output = LayerClassName(constructor_parameters)(previous_layer_output)
From which None1 is a constructor parameter value, and None2 would be the output of the previous layer in the model. Let us know if this helps?
ps: You might also want to take a look at the Functional API section of this related thread: Tips for troubles with Sequential and Functional API syntax