input: Write a function to compress a given data sequence by grouping consecutive numbers with the same sign together. If the sequence is empty, return an empty list.
  def compress_sequence(nums):
      if not nums:
          return []
      output = []
      temp = [nums[0]]
      for i in range(1, len(nums)):
          if (nums[i-1] >= 0 and nums[i] >= 0) or (nums[i-1] < 0 and nums[i] < 0):
              temp.append(nums[i])
          else:
              output.append(temp)
              temp = [nums[i]]
      output.append(temp)
      return output
  
  assert compress_sequence([9, -2, 6, 0, -7]) == [[9], [-2], [6, 0], [-7]]
  assert compress_sequence([]) == []
  assert compress_sequence([1, 2, 3, -1, -2, -3, 0, 0]) == [[1, 2, 3], [-1, -2, -3], [0, 0]]
  assert compress_sequence([0, 0, 0, -1, -1, -1, 1, 1, 1]) == [[0, 0, 0], [-1, -1, -1], [1, 1, 1]]
  assert compress_sequence([5]) == [[5]]
output: def compress_sequence(nums):
      if not nums:
          return []
      output = []
      temp = [nums[0]]
      for i in range(1, len(nums)):
          if (nums[i-1] >= 0 and nums[i] >= 0) or (nums[i-1] < 0 and nums[i] < 0):
              temp.append(nums[i])
          else:
              output.append(temp)
              temp = [nums[i]]
      output.append(temp)
      return output