input: Write a function named `slicing` that takes a string and two integers, `start` and `end`, as inputs and returns a substring sliced from the original string starting at `start` and ending at `end` (not inclusive).
  
  def slicing(string, start, end):
      return string[start:end]
  
  assert slicing("This is a slicing test", 8, 15) == "a slicing"
  assert slicing("Hello, world!", 7, 12) == "world"
  assert slicing("Python", 0, 6) == "Python"
  assert slicing("Challenge", 3, 6) == "lge"
  assert slicing("", 0, 0) == ""
output: def slicing(string, start, end):
      return string[start:end]