<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def single_val(self):

 """return relative error of worst point that might make the data none
 symmetric.
 """

        
        sv_t = self._sv(self._tdsphere)
        sv_p = self._sv(self._tdsphere)
        
        return (sv_t, sv_p)