code: def _format_value_error(self, v, e, pm=" +/- "):
          
          # If we have weird stuff
          if not _s.fun.is_a_number(v) or not _s.fun.is_a_number(e) \
              or v in [_n.inf, _n.nan, _n.NAN] or e in [_n.inf, _n.nan, _n.NAN]: 
              return str(v)+pm+str(e)
          
          # Normal values.
          try:
              sig_figs = -int(_n.floor(_n.log10(abs(e))))+1            
              return str(_n.round(v, sig_figs)) + pm + str(_n.round(e, sig_figs))
  
          except:
              return str(v)+pm+str(e)
docs: Returns a string v +/- e with the right number of sig figs.