def _concatenate(list_of_iters):
    """
    Return the concatenation of a list of iterables as a tuple.

    EXAMPLES::

        sage: from sage.combinat.multiset_partition_into_sets_ordered import _concatenate
        sage: L = ([1,2,3], Set([4,5,6]), [], range(7,11))
        sage: _concatenate(L)
        (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
    """
    return tuple([val for block in list_of_iters for val in block])