input: Write a function to slice a given string based on the provided start and end indices and return the sliced portion of the string. If the start index is negative or the end index is beyond the length of the string, return an empty string.
  assert slicing("Hello, world!", 7, 12)=="world"
  assert slicing("Python is fun", 10, 20)=="fun"
  assert slicing("Testing", -2, 5)==""
  assert slicing("Long string to slice", 0, 4)=="Long"
  assert slicing("Short", 5, 10)==""
output: def slicing(s, start, end):
      if start < 0 or end > len(s):
          return ""
      return s[start:end]