input: Write a Python function to invert each string within a specified list of string elements.
  assert invert_string_elements(['Red', 'Green', 'Blue', 'White', 'Black'])==['deR', 'neerG', 'eulB', 'etihW', 'kcalB']
  assert invert_string_elements(['john','amal','joel','george'])==['nhoj','lama','leoj','egroeg']
  assert invert_string_elements(['jack','john','mary'])==['kcaj','nhoj','yram']
output: def invert_string_elements(lst):
      return [s[::-1] for s in lst]