input: Write a function to generate all unique combinations of two elements from a list.
  assert generate_combinations([1, 2, 3, 4]) == [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
  assert generate_combinations([5, 6, 7]) == [(5, 6), (5, 7), (6, 7)]
  assert generate_combinations([10, 20]) == [(10, 20)]
  assert generate_combinations([1]) == []
output: def generate_combinations(lst):
      from itertools import combinations
      return list(combinations(lst, 2))