def get_provides exists Return list of available objects key_exists _e

def get_provides(exists):
    """ 
    Return list of available objects 
    """
    key_exists = _expand_exists(exists)
    superset = None
    for key in key_exists:
        if superset is None:
            superset = PROVIDES[key]
        superset = superset.union(PROVIDES[key])
    available = []
    for skey in superset:
        b = props.NewBuilding(*skey)
        if not get_requires(b, exists) and not skey in key_exists:
            available.append(skey)
    return available