code: func (g *Group) GetFirstElem(operand Operand) *list.Element {
  	if operand == OperandAny {
  		return g.Equivalents.Front()
  	}
  	return g.FirstExpr[operand]
  }
docs: // GetFirstElem returns the first Group expression which matches the Operand.
  // Return a nil pointer if there isn't.