input: def compress_sequence(nums):
      """
      Compresses a given data sequence by grouping elements that either are all positive or all negative together.
      >>> compress_sequence([9, -2, 6, 0, -7])
      [[9], [-2, 6], [0], [-7]]
      >>> compress_sequence([1, 2, 3, -1, -2, -3])
      [[1, 2, 3], [-1, -2, -3]]
      >>> compress_sequence([0, 0, 0])
      [[0, 0, 0]]
      """
      output = []
      temp = []
  
      for i in range(1, len(nums)):
          if nums[i-1] * nums[i] >= 0:
              temp.append(nums[i-1])
          else:
              temp.append(nums[i-1])
              output.append(temp)
              temp = []
      temp.append(nums[i])
      output.append(temp)
  
      return output
output:     output = []
      temp = []
  
      for i in range(1, len(nums)):
          if nums[i-1] * nums[i] >= 0:
              temp.append(nums[i-1])
          else:
              temp.append(nums[i-1])
              output.append(temp)
              temp = []
      temp.append(nums[i])
      output.append(temp)
  
      return output