input: Write a function to return the corresponding string for the given integer.
  assert get_string(1) == "One"
  assert get_string(2) == "Two"
  assert get_string(3) == "Three"
  assert get_string(4) == ""
output: def get_string(number):
      mapping = {
          1: "One",
          2: "Two",
          3: "Three"
      }
      return mapping.get(number, "")