code: function setLayerInGroupVisible(state, action) {
    const updated_layers = [];
    for (let i = 0, ii = state.layers.length; i < ii; i++) {
      const layer = state.layers[i];
      if (layer.metadata && layer.metadata[GROUP_KEY] === action.groupId) {
        updated_layers.push({
          ...layer,
          layout: {
            ...layer.layout,
            visibility: layer.id === action.layerId ? 'visible' : 'none',
          },
        });
      } else {
        updated_layers.push(layer);
      }
    }
    return Object.assign({}, state, {
      layers: updated_layers,
    }, incrementVersion(state.metadata, LAYER_VERSION_KEY));
  }
docs: Set a layer visible in a mutually exclusive group.
  @param {Object} state Current state.
  @param {Object} action Action to handle.
  
  @returns {Object} The new state.