[FPGADataFlow] Clean code

src/finn/transformation/fpgadataflow/prepare_cppsim.py

@@ -29,7 +29,6 @@
 import os
 
 import finn.custom_op.registry as registry
-from finn.transformation import Transformation
 from finn.util.basic import make_build_dir
 from finn.util.fpgadataflow import is_fpgadataflow_node
 from finn.transformation import Transformation
@@ -37,12 +36,13 @@ from finn.util.basic import get_num_default_workers
 import multiprocessing as mp
 import copy
 
+
 def _codegen_single_node(node, model):
     """Calls C++ code generation for one node. Resulting code can be used
     to simulate node using cppsim."""
 
     op_type = node.op_type
-    try: 
+    try:
         # lookup op_type in registry of CustomOps
         inst = registry.custom_op[op_type](node)
         # get the path of the code generation directory
@@ -85,7 +85,6 @@ class PrepareCppSim(Transformation):
             _codegen_single_node(node, self.model)
         return (node, False)
 
-
     def apply(self, model):
         # Remove old nodes from the current model
         self.model = copy.deepcopy(model)
@@ -106,4 +105,4 @@ class PrepareCppSim(Transformation):
             if run is True:
                 run_again = True
 
-        return (model, run_again)
+        return (model, run_again)
\ No newline at end of file