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[Gilbert Makgopa]

The function below prints "None" in between the output lines. Please assist.
Here is the results:

Name: Hemingway Ernest
None
Name: Madonna
None
Name: Voltaire
None

Function:
def format_name(first_name, last_name):
  # code goes here
  if (first_name != "" and last_name != ""):
     string = print("Name: " + last_name , first_name)
  elif (first_name == "" and last_name != ""):
     string = print("Name: " + last_name)

  elif (first_name != "" and last_name == ""):
     string = print("Name: " + first_name)

  elif (first_name == "" and last_name == ""):
     string = " "
  return string


print(format_name("Ernest", "Hemingway"))
# Should return the string "Name: Hemingway, Ernest"

print(format_name("", "Madonna"))
# Should return the string "Name: Madonna"

print(format_name("Voltaire", ""))
# Should return the string "Name: Voltaire"

print(format_name("", ""))
# Should return an empty string