def load_classes(filename):
    """
    This function takes in a class_file filename and returns a dict of classes and ids (in string format)

    :param filename: the filename of the class_file to load and parse
    :returns: a dict of classes and ids in string format
    """
    dict1 = {}
    f = open(filename,'r')
    classes = f.read().split('\n')[:-1]
    for value in classes:
        key, val = value.split(":")
        key =  key.strip(" ")
        val =  val.strip(" ")
        dict1[val] = key
    f.close()
    return dict1