09. Product List

# Define a procedure, product_list,
# that takes as input a list of numbers,
# and returns a number that is
# the result of multiplying all
# those numbers together.

def product_list(list_of_numbers):







#print product_list([9])
#>>> 9

#print product_list([1,2,3,4])
#>>> 24

#print product_list([])
#>>> 1