Now we'll create a function that creates the whole triangle structure, formatted as a list of lists. The first element will be the first

row $(n=0,$ a list that only contains the number $1),$ the second element will be the $n=1$ case $($the list containing $1$ and $1),$ etc.

More concretely, the value returned by pascal$\_$triangle$(3)$ should be the list $[[1],[1,1],[1,2,1],[1,3,3,1]].$

Note that indeed, this is a list of lists. Each element is a row of Pascal's triangle, with the zeroth row in the zeroth position.

Task

Finish implementing the function pascal$\_$triangle, started below.

It takes a single integer n as an argument, and generates a list of lists that represent Pascal's triangle to a specified a

depth of $n,$ as a list of lists, with the first being the zeorth row and the last being the nth row.

You will need to know that the first row is simply a single$-$element list with the number one: $[1].$

Subsequent rows should be able to be generated using the pascal$\_$row function you've already defined

Build up this list of lists in the provided tri variable, which is returned by the function.

For example,

print$($pascal$\_$triangle$(3))$

should return

$\left[\begin{array}{cccc}1& ?& ?& ?\\ 1& 1& ?& ?\\ 1& 2& 1& ?\\ 1& 3& 3& 1\end{array}\right]$

Save your resulting list of lists in the variable called tri.

In $[]$: v def pascal$\_$triangle$($n$)$:

Parametersn : int

the value of n for the last row to be printed. Must be greater than or equal to $0$

Returnslist of lists of integers

first row is the first row of Pascal's triangle $([1]).$ Last row is the nth row

where n is determined by $\text{'}$n$`$

$\text{'}\text{'}\text{'}$

tri $=[]$raise NotImplementedError$()$

return tri