input: Write a function to generate a multiplication table with numbers in a range given start and end parameters. If the start and end parameters are provided, the function should print the multiplication table for all numbers in that range, including both endpoints. If either of the parameters is missing, the function should return an error message.
  
  def multiplication_table(start, end):
  	if start is None or end is None:
  		return "Both start and end parameters are required."
  	for x in range(start, end + 1):
  		for y in range(start, end + 1):
  			print(x * y, end = "  ")
  		print("\n")
  		
  assert multiplication_table(5, 10) is None
  assert multiplication_table(1, 3) is None
  assert multiplication_table(0, 0) is None
  assert multiplication_table(10, 5) is None
  assert multiplication_table(None, 10) == "Both start and end parameters are required."
  assert multiplication_table(5, None) == "Both start and end parameters are required."
output: def multiplication_table(start, end):
  	if start is None or end is None:
  		return "Both start and end parameters are required."
  	for x in range(start, end + 1):
  		for y in range(start, end + 1):
  			print(x * y, end = "  ")
  		print("\n")