code: function setContext(state, action) {
    let metadata = incrementVersion(state.metadata, SOURCE_VERSION_KEY);
    metadata = incrementVersion(metadata.metadata, LAYER_VERSION_KEY);
    return Object.assign({}, action.context, {
      metadata: Object.assign({}, metadata.metadata, action.context.metadata)
    });
  }
docs: Load a new context
  @param {Object} state Current state.
  @param {Object} action Action to handle.
  
  @returns {Object} The new state.