[Test] fix incorrect import in test_channelslast

Author: maltanar

tests/transformation/test_channelslast.py

@@ -33,7 +33,7 @@
 import qonnx.core.onnx_exec as oxe
 from qonnx.core.modelwrapper import ModelWrapper
 from qonnx.custom_op.channels_last.base_wrapped_op import to_channels_last_args
-from qonnx.custom_op.registry import get_ops_in_domain, getCustomOp
+from qonnx.custom_op.registry import get_ops_in_domain, getCustomOp, is_custom_op
 from qonnx.transformation.channels_last import (
     AbsorbChanFirstIntoMatMul,
     InsertChannelsLastDomainsAndTrafos,
@@ -46,7 +46,6 @@
 from qonnx.transformation.infer_shapes import InferShapes
 from qonnx.transformation.make_input_chanlast import MakeInputChannelsLast
 from qonnx.transformation.quant_constant_folding import FoldTransposeIntoQuantInit
-from qonnx.util.basic import is_custom_op
 from qonnx.util.test import download_model, get_golden_in_and_output, test_model_details
 from qonnx.util.to_channels_last import to_channels_last