code: def _fmt_exp(cls, x, **kw):
          
          n = kw.get('n')
          return '%.*e' % (n, cls._to_float(x))
docs: Exponential formatting class-method.
  
          - x parameter is ignored. Instead kw-argument f being x float-converted
            will be used.
  
          - precision will be taken from `n` kw-argument.