input: Write a function to return a slice of a given string using the provided start and end indices. The function should take three parameters: the string, the start index, and the end index. It should then return the substring from the start index to the end index.
  assert slicing("This is a slicing test", 8, 15)=="a slicing"
output: def slicing(s, start, end):
      return s[start:end]