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.
code: def elapsed_time():
      seconds = time.time() - TimerMagic.start_time
      minutes = seconds // 60
      hours = minutes // 60
      return "Timer elapsed: %02d:%02d:%02d" % (
          hours,
          minutes % 60,
          seconds % 60,
      )
  
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 1 for calling the TimerMagic obj's underlying member method code with example usage: obj.elapsed_time() and returns: unknown