def flatten(myList, newList):

for element in myList:

if isinstance(element, list): #check type of elements. list or not.

flatten(element, newList) #if it is list, then turn back to flatten function.

else:

newList.append(element) #otherwise add the element to newList.

return newList

print(flatten([[1,'a',['cat'],2],[[[3]],'dog'],4,5], []))

#######################################################################

def reverse_nested_list(myList):

output = []

for element in myList:

if isinstance(element, list):

output.append(reverse_nested_list(element))

else:

output.append(element)

output.reverse()

return output

example = [[1, 2], [3, 4], [5, 6, 7]]

reversed(example)