What does the error "NameError" mean while evaluating `PySide6.QtWidgets.QWidget.__init__`, indicating that the name 'PySide6' is undefined?

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The error "NameError" means that the name 'PySide6' is undefined in the current scope, i.e., it has not been defined or imported before. This can happen if PySide6 module is not installed or if it has not been imported in the script where this error is occurring. To resolve this error, make sure that PySide6 is installed and imported in the script before instantiating the QWidget class.