docs: def copy_abs(self):
          """ Return a copy of self with the sign bit unset.
  
          Unlike abs(self), this does not make use of the context: the result
          has the same precision as the original.
  
          """
          result = mpfr.Mpfr_t.__new__(BigFloat)
          mpfr.mpfr_init2(result, self.precision)
          mpfr.mpfr_setsign(result, self, False, ROUND_TIES_TO_EVEN)
          return result