code: async function addStream(call, propertyPath, addStreamCallback) {
              return _addStream(client, call, propertyPath, addStreamCallback);
          }
docs: This callback that is called after attempting to add a call to the stream
  @callback addStreamCallback
  @param {null|Error} error Lets the caller know if there was an error adding the call to the stream
  @param {stream} The stream that was added
   
  Adds an call to the continuous update stream.
  @name addStream
  @param {procedureCall} procedureCall The call to add to the stream
  @param {string} propertyPath A unique name to represent the call
  @param {addStreamCallback} [callback] the callback function to execute when the operation has ended
  @returns {Promise.<stream>} The stream that was added