Scope `onnx-simplifier` requirements check (#4730)

* Changed onnx-simplifier check behavior Export.py has been updated to check for onnx-simplifier requirement only when the --simplify argument is added. Allows for better flexibility and one less requirement if simplify is not needed. * Fix single-element tuples Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

Scope `onnx-simplifier` requirements check (#4730)
2d9411db · Zegorax · GitHub · 1cad0ce2 · 2d9411db
--- a/export.py
+++ b/export.py
@@ -44,7 +44,7 @@ def export_onnx(model, img, file, opset, train, dynamic, simplify):
    # ONNX model export
    prefix = colorstr('ONNX:')
    try:
-        check_requirements(('onnx', 'onnx-simplifier'))
+        check_requirements(('onnx',))
        import onnx
        print(f'\n{prefix} starting export with onnx {onnx.__version__}...')
@@ -66,6 +66,7 @@ def export_onnx(model, img, file, opset, train, dynamic, simplify):
        # Simplify
        if simplify:
            try:
+                check_requirements(('onnx-simplifier',))
                import onnxsim
                print(f'{prefix} simplifying with onnx-simplifier {onnxsim.__version__}...')