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 option_completer(cls, k, v):
      return ["start"]
  
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 2 for calling the TimerMagic obj's underlying member method code with example usage: obj.option_completer(cls, k, v) and returns: list