def get_atomtrailer_list(r):
    """Capture only the leading dotted name list.

    A full sequence typically includes function calls and parameters.
    pkg_a.pkg_b.pkg_c.one_call(arg1, arg2, arg3=4)

    """
    dot_set = set()
    for n in r.find_all(('atomtrailers',)):
        name_list = []
        for x in n.value:
            if x.type != 'name':
                break
            name_list.append(x.value)
        if name_list:
            dot_set.add(tuple(name_list))
    return sorted(dot_set)
