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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 _validate_bagittxt(self):
 """ Verify that bagit.txt conforms to specification """

        bagit_file_path = os.path.join(self.path, "bagit.txt")
        with open(bagit_file_path, 'r') as bagit_file:
            first_line = bagit_file.readline()
            if first_line.startswith(BOM):
                raise BagValidationError("bagit.txt must not contain a byte-order mark")