code: function getStreamProcessingFunction(context, settingName) {
    const fn = getStreamProcessingSetting(context, settingName);
    return typeof fn === 'function' ? fn : undefined;
  }
docs: Returns the function configured at the named stream processing setting on the given context (if any and if it's a
  real function); otherwise returns undefined.
  @param {StreamProcessing} context - the context from which to fetch the function
  @param {string} settingName - the name of the stream processing setting
  @returns {Function|undefined} the named function (if it's a function); otherwise undefined