class_docstr: Window operator
  
  inputs:       ---1--2-3-----4-5-6--->
  timestamp:    0 ------1000ms-------2000ms---->
  
  node definition:
  
    [    time_window('input', 'output', time_range_sec=1, time_step_sec=1, timestamp_col: 'timestamp', callable=lambda i: sum(i))     ]
  
  windows: [0s, 1s) [1s, 2s)
  every step:
  
    callable([1, 2, 3]) -> 6
    callable([4, 5, 6]) -> 15
  
  outputs:
    ----6-----15------->
class_docstr_tok: ["Window","operator","inputs",":","--","-1","--","2-3","--","--","-4-5-6","--","-",">","timestamp",":","0","--","--","--","1000ms","--","--","--","-2000ms","--","--",">","node","definition",":","[","time_window","(","'input","'",",","'output","'",",","time_range_sec=1",",","time_step_sec=1",",","timestamp_col",":","'timestamp","'",",","callable=lambda","i",":","sum","(","i",")",")","]","windows",":","[","0s",",","1s",")","[","1s",",","2s",")","every","step",":","callable","(","[","1",",","2",",","3","]",")","-",">","6","callable","(","[","4",",","5",",","6","]",")","-",">","15","outputs",":","--","--","6","--","--","-15","--","--","--","-",">"]
code: def _window_index(self, data):
      timestamp = data[self._timestamp_index]
      if timestamp is Empty():
          return -1
      return timestamp
  
file_path: towhee/towhee/runtime/nodes/_time_window.py
imports: from towhee.runtime.constants import TimeWindowConst
  from towhee.runtime.data_queue import Empty
  from ._window_base import WindowBase
label_desc: Use image node_id 2 for calling the TimeWindow obj's underlying member method code with example usage: obj._window_index(data) and returns: timestamp, unknown