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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def attach_foreignkey(objects, field, related=[], database=None):
 """ Shortcut method which handles a pythonic LEFT OUTER JOIN. ``attach_foreignkey(posts, Post.thread)`` Works with both ForeignKey and OneToOne (reverse) lookups. """


    if not objects:
        return

    if database is None:
        database = list(objects)[0]._state.db

    is_foreignkey = isinstance(field, SingleRelatedObjectDescriptor)

    if not is_foreignkey:
        field = field.field
        accessor = '_%s_cache' % field.name
        model = field.rel.to
        lookup = 'pk'
        column = field.column
        key = lookup
    else:
        accessor = field.cache_name
        field = field.related.field
        model = field.model
        lookup = field.name
        column = 'pk'
        key = field.column

    objects = [o for o in objects if (related or getattr(o, accessor, False) is False)]

    if not objects:
        return

    # Ensure values are unique, do not contain already present values, and are not missing
    # values specified in select_related
    values = distinct(filter(None, (getattr(o, column) for o in objects)))
    if values:
        qs = model.objects.filter(**{'%s__in' % lookup: values})
        if database:
            qs = qs.using(database)
        if related:
            qs = qs.select_related(*related)

        queryset = queryset_to_dict(qs, key=key)
    else:
        queryset = {}

    for o in objects:
        setattr(o, accessor, queryset.get(getattr(o, column)))