docs: def copy(self):
          """ Return a copy of self.
  
          This function 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_set(result, self, ROUND_TIES_TO_EVEN)
          return result