Write a Python function named multiplication_table that takes a value n and returns an n by n multiplication table. For instance, if n is seven, your program will return a table as follows. 12 3 4 5 6 8 10 3 6 9 12 15 18 4 8 12 16 20 24 28 5 10 15 20 25 30 35 6 12 18 24 30 36 42 7 14 21 28 35 42 49 The first element of the nested list should be a list that represents the first row of the table, the second element represents the second row and so on. For n < 1, your function should return the value None. 123 2 6 7 12 14 21 246