You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: history_func.go
    path of file: ./repos/mgmt/lang/funcs
    
    the code of the file until where you have to start completion: // Mgmt
// Copyright (C) 2013-2024+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
    
func (obj *HistoryFunc) Polymorphisms(partialType *types.Type, partialValues []types.Value) ([]*types.Type, error) {
	// TODO: return `variant` as first & return arg for now -- maybe there's a better way?
	variant := []*types.Type{types.NewType("func(value variant, index int) variant")}

	if partialType == nil {
		return variant, nil
	}

	var typ *types.Type // = nil is implied

	ord := partialType.Ord
	if partialType.Map != nil {
		if len(ord) != 2 {
			return nil, fmt.Errorf("must have at exactly two args in history func")
		}
		if t, exists := partialType.Map[ord[1]]; exists && t != nil {
			if t.Cmp(types.TypeInt) != nil {
				return nil, fmt.Errorf("second arg for history must be an int")
			}
		}

		if t, exists := partialType.Map[ord[0]]; exists && t != nil && partialType.Out != nil {
			if t.Cmp(partialType.Out) != nil {
				return nil, fmt.Errorf("type of first arg for history must match return type")
			}
			typ = t // it has been found :)
		}
	}

	if partialType.Out != nil {
		typ = partialType.Out // it has been found :)
	}

	if typ == nil {
		return variant, nil
	}

	t := types.NewType(fmt.Sprintf("func(value %s, index int) %s", typ.String(), typ.String()))

	return []*types.Type{t}, nil // return a list with a single possibility
}