Merge in undefined list entries from given list.
    
    @param l: List to be merged into.
    @type l: list
    
    @param base: List to be merged into.
    @type base: list

def merge_lists(l, base):
    """
    Merge in undefined list entries from given list.
    
    @param l: List to be merged into.
    @type l: list
    
    @param base: List to be merged into.
    @type base: list
    """
    
    for i in base:
        if i not in l:
            l.append(i)