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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_int(self):
 """Convert vector to an integer, if possible. This is only useful for arrays filled with zero/one entries. """

        num = self.to_uint()
        if num and self._items[-1].unbox():
            return num - (1 << self.size)
        else:
            return num