def linear_search(list_to_search_in, key_to_search_for, field = lambda item: item["title"]):
    """
        Does a linear search through a list.
        Defaults to searching for "title" if no other field is specified.
    """

    if len(list_to_search_in) == 0 or key_to_search_for == None:
        return "Error"

    #list to put all found items in
    list_with_found_items = []

    #go through every item in the list
    for item in list_to_search_in:
        #if the search key is in list[field], append to list and go on
        if str(key_to_search_for).lower() in str(field(item)).lower():
            list_with_found_items.append(item)
            continue
    return list_with_found_items