human
Complete this python program:
def initialize_dependencies(bears):
assistant
#Here is the Python program you requested.

    """Initializes and returns a ``DependencyTracker`` instance together with a
    set of bears ready for scheduling.
    This function acquires, processes and registers bear dependencies
    accordingly using a consumer-based system, where each dependency bear has
    only a single instance per section and file-dictionary.
    The bears set returned accounts for bears that have dependencies and
    excludes them accordingly. Dependency bears that have themselves no further
    dependencies are included so the dependency chain can be processed
    correctly.
    :param bears:
    The set of instantiated bears to run that serve as an entry-point.
    :return:
    A tuple with ``(dependency_tracker, bears_to_schedule)``.
    """
    bears = set(bears)
    dependency_tracker = DependencyTracker()
    grouping = group(bears, key=(lambda bear: (bear.section, bear.file_dict)))
    for ((section, file_dict), bears_per_section) in grouping:
        bears_per_section = list(bears_per_section)
        type_to_instance_map = {}
        for bear in bears_per_section:
            type_to_instance_map[bear] = bear
            type_to_instance_map[type(bear)] = bear
        def instantiate_and_track(prev_bear_type, next_bear_type):
            if (next_bear_type not in type_to_instance_map):
                type_to_instance_map[next_bear_type] = next_bear_type(section, file_dict)
            dependency_tracker.add(type_to_instance_map[next_bear_type], type_to_instance_map[prev_bear_type])
        traverse_graph(bears_per_section, (lambda bear: bear.BEAR_DEPS), instantiate_and_track)
    bears -= {bear for bear in bears if dependency_tracker.get_dependencies(bear)}
    for dependency in dependency_tracker.dependencies:
        if (not dependency_tracker.get_dependencies(dependency)):
            bears.add(dependency)
    return (dependency_tracker, bears)