def pathfinder(instance, filename):
    """Defining upload path's for upload_to= in Imagefield's as lambdas proved unpredictable with migrations."""

    if instance.__class__.__name__ == 'Concept':
        return f'concepts/{slugify(instance.name)}/{filename}'
    elif instance.__class__.__name__ == 'Category':
        return f'Categories/{slugify(instance.name)}/{filename}'
    elif instance.__class__.__name__ == 'Subcategory':
        return f'subcategories/{slugify(instance.name)}/{filename}'
    elif instance.__class__.__name__ == 'Supplier':
        return f'suppliers/{slugify(instance.name)}/{filename}'
    elif instance.__class__.__name__ == 'Manufacturer':
        return f'manufacturers/{slugify(instance.name)}/{filename}'
    elif instance.__class__.__name__ == 'Item':
        return f'items/{slugify(instance.part_number)}/{filename}'