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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 hex(self):
 """Return a hexadecimal representation of a BigFloat."""


        sign = '-' if self._sign() else ''
        e = self._exponent()
        if isinstance(e, six.string_types):
            return sign + e

        m = self._significand()
        _, digits, _ = _mpfr_get_str2(
            16,
            0,
            m,
            ROUND_TIES_TO_EVEN,
        )
        # only print the number of digits that are actually necessary
        n = 1 + (self.precision - 1) // 4
        assert all(c == '0' for c in digits[n:])
        result = '%s0x0.%sp%+d' % (sign, digits[:n], e)
        return result