code: def to_qubo(self):
          
          qubo = dict(self.binary.quadratic)
          qubo.update(((v, v), bias) for v, bias in iteritems(self.binary.linear))
          return qubo, self.binary.offset
docs: 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.
  
              >>> import dimod
              >>> model = dimod.BinaryQuadraticModel({0: 1, 1: -1, 2: .5},
              ...                                    {(0, 1): .5, (1, 2): 1.5},
              ...                                    1.4,
              ...                                    dimod.SPIN)
              >>> model.to_qubo()   # doctest: +SKIP
              ({(0, 0): 1.0, (0, 1): 2.0, (1, 1): -6.0, (1, 2): 6.0, (2, 2): -2.0}, 2.9)