code: function getImpressionEventParams(configObj, experimentId, variationId) {
    var impressionEventParams = {
        decisions: [{
          campaign_id: projectConfig.getLayerId(configObj, experimentId),
          experiment_id: experimentId,
          variation_id: variationId,
        }],
        events: [{
          entity_id: projectConfig.getLayerId(configObj, experimentId),
          timestamp: fns.currentTimestamp(),
          key: ACTIVATE_EVENT_KEY,
          uuid: fns.uuid(),
        }]
  
      };
    return impressionEventParams;
  }
docs: Creates object of params specific to impression events
  @param  {Object} configObj    Object representing project configuration
  @param  {string} experimentId ID of experiment for which impression needs to be recorded
  @param  {string} variationId  ID for variation which would be presented to user
  @return {Object}              Impression event params