def walk_service_sources(b, manager, servicename, **kwargs):
    """
    Walk a service's source tarball dependencies and execute callbacks.

    * `service_source(manager, servicename, dirname):`
      Executed when a source tarball service dependency is enumerated.
    """
    deps = b.get('services', {}).get(manager, {}).get(servicename, {})
    if deps not in 'sources':
        return
    callable = kwargs.get('service_source', lambda *args: None)
    for dirname in list(deps['sources']):
        callable(manager, servicename, dirname)
dataset/ETHPy150Open devstructure/blueprint/blueprint/walk.py/walk_service_sources/swapped operands of `not in`