concat
======
Returns the concatenation of output.

Function Arguments
------------------
.. list-table::
   :widths: 20 10 60
   :header-rows: 1
   :align: left

   * - Name
     - Type
     - Description

   * - functions
     - list
     - The list of the function expression.

Description
-----------
Concat the outputs of the functions.
The type of all the outputs of functions must be a list.
The concept is::

  res = []
  res.extend(Func1(data))
  res.extend(Func2(data))
  ...