input: Write a python function to generate all permutations of a list of numbers.
  assert generate_permutations(['1', '2', '3']) == ['123', '132', '213', '231', '321', '312']
  assert generate_permutations(['a', 'b']) == ['ab', 'ba']
  assert generate_permutations(['x']) == ['x']
output: def generate_permutations(lst):
      from itertools import permutations
      perm = permutations(lst)
      return [''.join(p) for p in perm]