input: Write a function to slice a given string using a start and end index, and return the extracted substring.
  def slicing(string, start, end):
      return string[start:end]
  
  assert slicing("This is a slicing test", 8, 15) == "slicing"
  assert slicing("Python Programming", 7, 18) == "Programming"
  assert slicing("Hello World", 0, 5) == "Hello"
  assert slicing("Testing 123", 8, 11) == "123"
  assert slicing("", 0, 0) == ""
output: def slicing(string, start, end):
      return string[start:end]