title: convert a 2d array of integers into string python
body: <p>convert a 2d array of integers into String. For example myArray = [[1,2,3],[3,4,5]] into   myArrayL = [[a,b,c],[c,d,e]]
   and retain the shape of the 2d array</p>
  
  <p>where 1 = "a" , 2 = "b", 3 = "c"</p>