class_docstr: A line magic for measuring the execution time of multiple cells.
  
  After you start/reset the timer with '%timer start' you may view
  elapsed time with any subsequent calls to %timer.
docstr: Timer magic to print initial date/time information and
  subsequent elapsed time intervals.
  
  To start the timer, run:
  
  %timer start
  
  This will print the start date and time.
  
  Subsequent calls to %timer will print the elapsed time
  relative to the time when %timer start was called. Subsequent
  calls to %timer start may also be used to reset the timer.
docstr_tok: ["Timer","magic","to","print","initial","date\/time","information","and","subsequent","elapsed","time","intervals",".","To","start","the","timer",",","run",":","%","timer","start","This","will","print","the","start","date","and","time",".","Subsequent","calls","to","%","timer","will","print","the","elapsed","time","relative","to","the","time","when","%","timer","start","was","called",".","Subsequent","calls","to","%","timer","start","may","also","be","used","to","reset","the","timer","."]
code: def timer(self, line=""):
      """
      Timer magic to print initial date/time information and
      subsequent elapsed time intervals.
  
      To start the timer, run:
  
      %timer start
  
      This will print the start date and time.
  
      Subsequent calls to %timer will print the elapsed time
      relative to the time when %timer start was called. Subsequent
      calls to %timer start may also be used to reset the timer.
      """
      if line.strip() not in ["", "start"]:
          print(
              "Invalid argument to %timer. For more information consult %timer?"
          )
          return
      elif line.strip() == "start":
          TimerMagic.start_time = time.time()
          timestamp = time.strftime("%Y/%m/%d %H:%M:%S")
          print(f"Timer start: {timestamp}")
          return
      elif self.start_time is None:
          print(
              "Please start timer with %timer start. For more information consult %timer?"
          )
      else:
          print(self.elapsed_time())
  
imports: import sys
  import time
  from IPython.core.magic import Magics, line_cell_magic, line_magic, magics_class
  from IPython.display import HTML, display
  from ..core.options import Options, Store, StoreOptions, options_policy
  from ..core.pprint import InfoPrinter
  from ..operation import Compositor
  from IPython.core import page
label_desc: Use image node_id 3 for calling the TimerMagic obj's underlying member method code with example usage: obj.timer(line) without return types