input: def compress_sequence(nums: List[int]) -> List[List[int]]:
      """ Compress a given data sequence by grouping consecutive numbers of the same sign.
      >>> compress_sequence([9, -2, 6, 0, -7])
      [[9], [-2], [6, 0], [-7]]
      """
output:     result = []
      if not nums:
          return result
      
      current_group = [nums[0]]
      
      for num in nums[1:]:
          if (num >= 0 and current_group[-1] >= 0) or (num < 0 and current_group[-1] < 0):
              current_group.append(num)
          else:
              result.append(current_group)
              current_group = [num]
      
      result.append(current_group)
      return result