code: function clusterPoints(state, action) {
    const source = state.sources[action.sourceName];
    if (!source) {
      return state;
    }
    const src_mixin = [];
    const cluster_settings = {};
  
    if (typeof action.cluster !== 'undefined') {
      cluster_settings.cluster = action.cluster;
      // Mapbox GL style spec defaults to 50,
      //  whereas OpenLayers defaults to 20px.
      cluster_settings.clusterRadius = source.clusterRadius ? source.clusterRadius : 50;
    }
  
    // The radius can be overridden at any time.
    if (typeof action.radius !== 'undefined') {
      cluster_settings.clusterRadius = action.radius;
    }
    src_mixin[action.sourceName] = Object.assign({}, source, cluster_settings);
  
    const newState = Object.assign({}, state, {
      sources: Object.assign({}, state.sources, src_mixin),
    }, incrementVersion(state.metadata, SOURCE_VERSION_KEY));
    return newState;
  }
docs: Cluster points.
  @param {Object} state Current state.
  @param {Object} action Action to handle.
  
  @returns {Object} The new state.