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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 build(self):
 """Builds the barcode pattern from 'self.upc' :return: The pattern as string :rtype: String """

        code = _upc.EDGE[:]

        for i, number in enumerate(self.upc[0:6]):
            code += _upc.CODES['L'][int(number)]

        code += _upc.MIDDLE

        for number in self.upc[6:]:
            code += _upc.CODES['R'][int(number)]

        code += _upc.EDGE

        return [code]