Add fix for Tensorflow python bindings if we cannot determine output_fields

src/pystencils_autodiff/backends/python_bindings.py

@@ -90,7 +90,7 @@ REGISTER_KERNEL_BUILDER(Name("{{ python_name }}").Device({{ device }}), {{ pytho
         """  # noqa
     )
 
-    required_global_declarations = ["using namespace tensorflow;"]
+    required_global_declarations = [CustomCodeNode("using namespace tensorflow;", (), ())]
     headers = ['"tensorflow/core/framework/op.h"',
                '"tensorflow/core/framework/op_kernel.h"']
 
@@ -100,7 +100,11 @@ REGISTER_KERNEL_BUILDER(Name("{{ python_name }}").Device({{ device }}), {{ pytho
         input_field_names = [f.name for f in input_fields]
         output_field_names = [f.name for f in output_fields]
         parameters = function_node.get_parameters()
-        output_shape = str(output_fields[0].shape).replace('(', '{').replace(')', '}')  # noqa,  TODO make work for flexible sizes
+        if not output_fields:
+            output_shape = str(next(iter(function_node.fields_accessed)).shape).replace('(', '{').replace(')', '}')  # noqa,  TODO make work for flexible sizes
+            input_fields = function_node.fields_accessed
+        else:
+            output_shape = str(output_fields[0].shape).replace('(', '{').replace(')', '}')  # noqa,  TODO make work for flexible sizes
 
         docstring = "TODO"  # TODO