def composite_get_choices_dict(field_list):
    """
    Converts a list of dictionaries containing the keys
    "field_name" and "choices" into a single dictionary
    with "field_name" value as key and "choices" as value.
    If choices is not defined, then an empty list is assigned.
    """
    choices_dict = {}
    for field in field_list:
        name = field.get('field_name', '')
        choices_dict[name] = field.get('choices', [])
    return choices_dict
