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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_errors(self):
 """Verify that this MAR file is well formed. Returns: A list of strings describing errors in the MAR file None if this MAR file appears well formed. """

        errors = []
        errors.extend(self._get_signature_errors())
        errors.extend(self._get_additional_errors())
        errors.extend(self._get_entry_errors())

        return errors if errors else None