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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 to_qubo(self):
 """Convert a binary quadratic model to QUBO format. If the binary quadratic model's vartype is not :class:`.Vartype.BINARY`, values are converted. Returns: tuple: 2-tuple of form (`biases`, `offset`), where `biases` is a dict in which keys are pairs of variables and values are the associated linear or quadratic bias and `offset` is a number that represents the constant offset of the binary quadratic model. Examples: This example converts a binary quadratic model with spin variables to QUBO format with binary variables. ({(0, 0):
 1.0, (0, 1):
 2.0, (1, 1):
 -6.0, (1, 2):
 6.0, (2, 2):
 -2.0}, 2.9) """

        qubo = dict(self.binary.quadratic)
        qubo.update(((v, v), bias) for v, bias in iteritems(self.binary.linear))
        return qubo, self.binary.offset