def population_filter(neighbors, min_population):
    """Drop key-index pairs with insufficient populations.

    Parameters
    ----------
    neighbors : dict
        Key-index mappings.

    min_population : int
        Minimum number of items to keep, inclusive.

    Returns
    -------
    filt_neighbors : dict
        Population-filtered key-index mappings.
    """
    nbs = {}
    keys = list(neighbors.keys())
    for k in keys:
        if len(neighbors[k]) >= min_population:
            nbs[k] = neighbors[k]
    return nbs