input: Write a function to perform string slicing that takes a string and start and end indices, and returns the sliced substring.
  
  def slicing(string, start, end):
      return string[start:end]
  
  assert slicing("This is a slicing test", 8, 15)=="slicing"
  assert slicing("Python is fun!", 7, 9)=="is"
  assert slicing("Hello, World!", 0, 5)=="Hello"
  assert slicing("String manipulation", 15, 21)=="nt"
  assert slicing("", 0, 0)==""
output: def slicing(string, start, end):
      return string[start:end]