h distinct
    value in the input array.

    >>> val_indices.keys()
    dict_keys([0, 1, 2, 3])

    The entry for each value is an index tuple, locating the elements
    with that value.

    >>> ndx1 = val_indices[1]
    >>> ndx1
    (array([2, 2, 3, 3, 4]), array([2, 3, 2, 3, 4]))

    This can be used to index into the original array, or any other
    array with the same shape.

    >>> a[ndx1]
    array([1, 1, 1, 1, 1])

    If the zeros were to be ignored, then the resulting dictionary
    would no longer have an entry for zero.

    >>> val_indices = ndimage.value_indices(a, ignore_value=0)
    >>> val_indices.keys()
    dict_keys([1, 2, 3])

    )