code: func (e *gfP12) Frobenius(a *gfP12, pool *bnPool) *gfP12 {
  	e.x.Frobenius(a.x, pool)
  	e.y.Frobenius(a.y, pool)
  	e.x.MulScalar(e.x, xiToPMinus1Over6, pool)
  	return e
  }
docs: // Frobenius computes (xω+y)^p = x^p ω·ξ^((p-1)/6) + y^p