Write a function called possibly$\_$orf which takes a single argument called rna $($expected to be a string representing an RNA sequence$).$ The purpose of this function is to determine if the provided RNA sequence is a valid ORF. The function should perform the following tasks:

a$.$ Check if the length of the string is a multiple of three. If so$,$ the function should continue to the next step, otherwise the function should print The length of the sequence is not a multiple of three. and return False. Recall that the modulus operator $\%$ is useful for doing this type of check!

b$.$ Check if the first three letters are AUG. If so$,$ the function should continue to the next step, otherwise the function should print The first codon is not AUG. and return False.