def h3_to_children(h3_index, child_resolution)
      max_children = max_h3_to_children_size(h3_index, child_resolution)
      out = H3Indexes.of_size(max_children)
      Bindings::Private.h3_to_children(h3_index, child_resolution, out)
      out.read
    end
def h3_to_children(h3_index, child_resolution)
      max_children = max_h3_to_children_size(h3_index, child_resolution)
      out = H3Indexes.of_size(max_children)
      Bindings::Private.h3_to_children(h3_index, child_resolution, out)
      out.read
    end
Derive child hexagons contained within the hexagon at the given H3 index.

 @param [Integer] h3_index A valid H3 index.
 @param [Integer] child_resolution The desired resolution of hexagons returned.

 @example Find the child hexagons for a H3 index.
   H3.h3_to_children(613196570357137407, 9)
   [
     617700169982672895, 617700169982935039, 617700169983197183, 617700169983459327,
     617700169983721471, 617700169983983615, 617700169984245759
   ]

 @return [Array<Integer>] H3 indexes of child hexagons.