Write a custom function CheckSquare$()$ to check if a $2$D array is square. A $2$D array is square if the number of rows equals the number of columns. CheckSquare will be used in the following manner:

$\backslash$table$[[,\backslash$table$[[$testmat $1,],[4,3],[2,1]]],[\backslash$table$[[$testMat $1=[4,3$;$2,1]$