text: import os
  import re
  
  from contextlib import contextmanager
  from cProfile import Profile
  from functools import wraps
  from pstats import Stats
  
  from tornado.template import Template
  
  from ..util import escape
  from .state import state
  
  
  def render_pyinstrument(sessions, timeline=False, show_all=False):
      from pyinstrument.session import Session
      from pyinstrument.renderers import HTMLRenderer
      r = HTMLRenderer(timeline=timeline, show_all=show_all)
      session = sessions[0]
      if not timeline:
          for s in sessions[1:]:
              session = Session.combine(session, s)
      return escape(r.render(session)), ""
  
  
  def render_snakeviz(name, sessions):
      import snakeviz
      from snakeviz.stats import json_stats, table_rows
      SNAKEVIZ_PATH = os.path.join(os.path.dirname(snakeviz.__file__), 'templates', 'viz.html')
      with open(SNAKEVIZ_PATH) as f:
          SNAKEVIZ_TEMPLATE = Template(f.read())
      pstats = Stats(sessions[0])
      for session in sessions[1:]:
          pstats.add(session)
      rendered = SNAKEVIZ_TEMPLATE.generate(
          profile_name=name, table_rows=table_rows(pstats), callees=json_stats(pstats)
      ).decode('utf-8').replace('/static/', '/snakeviz/static/')
      return escape(rendered), "background-color: white;"
  
  
  def get_profiles(profilers, **kwargs):
      from ..pane import HTML, Markdown
      profiles = []
      for (path, engine), sessions in profilers.items():
          if not sessions:
              continue
          if engine == 'pyinstrument':
              src, style = render_pyinstrument(sessions, **kwargs)
          elif engine == 'snakeviz':
              src, style = render_snakeviz(path, sessions)
          html = HTML(
              f'<iframe srcdoc="{src}" width="100%" height="100%" frameBorder="0" style="{style}"></iframe>',
              sizing_mode='stretch_both',
              margin=0,
              min_height=400
          )
          profiles.append((path, html))
      if not profiles:
          profiles.append(('', Markdown('No profiling output available')))
      return profiles
  
  
  def get_sessions(allow=None, deny=None):
      return {(name, e): ps for (name, e), ps in state._profiles.items()
              if (not allow or re.match(allow, name)) and (not deny or not re.match(deny, name))}
  
  
  def profiling_tabs(state, allow=None, deny=[]):
      from ..layout import Accordion, Column, Row, Tabs
      from ..widgets import Checkbox
      tabs = Tabs(
          *get_profiles(get_sessions(allow, deny)),
          margin=(0, 5),
          sizing_mode='stretch_width'
      )
      def update_profiles(*args):
          tabs[:] = get_profiles(
              get_sessions(allow, deny),
              timeline=timeline.value,
              show_all=show_all.value
          )
      state.param.watch(update_profiles, '_profiles')
      timeline = Checkbox(name='Enable timeline', margin=(5, 0))
      timeline.param.watch(update_profiles, 'value')
      show_all = Checkbox(name='Show All', margin=(5, 0))
      show_all.param.watch(update_profiles, 'value')
      return Column(
          Accordion(
              ('Config', Row(
                  timeline,
                  show_all,
                  sizing_mode='stretch_width'
              )),
              active=[],
              active_header_background='#444444',
              header_background='#333333',
              sizing_mode='stretch_width',
              margin=0
          ),
          tabs,
          sizing_mode='stretch_width'
      )
  
  
  @contextmanager
  def profile_ctx(engine='pyinstrument'):
      """
      A context manager which profiles the body of the with statement
      with the supplied profiling engine and returns the profiling object
      in a list.
  
      Arguments
      ---------
      engine: str
        The profiling engine, e.g. 'pyinstrument' or 'snakeviz' 
  
      Returns
      -------
      sessions: list
        A list containing the profiling session.
      """
      if engine == 'pyinstrument':
          from pyinstrument import Profiler
          try:
              prof = Profiler()
              prof.start()
          except RuntimeError:
              prof = Profiler(async_mode='disabled')
              prof.start()
      elif engine == 'snakeviz':
          prof = Profile()
          prof.enable()
      elif engine is None:
          pass
      sessions = []
      yield sessions
      if engine == 'pyinstrument':
          sessions.append(prof.stop())
      elif engine == 'snakeviz':
          prof.disable()
          sessions.append(prof)
  
  
  def profile(name, engine='pyinstrument'):
      """
      A decorator which may be added to any function to record profiling
      output.
  
      Arguments
      ---------
      name: str
        A unique name for the profiling session.
      engine: str
        The profiling engine, e.g. 'pyinstrument' or 'snakeviz' 
      """
      if not isinstance(name, str):
          raise ValueError("Profiler must be given a name.")
      def wrapper(func):
          @wraps(func)
          def wrapped(*args, **kwargs):
              if state.curdoc and state.curdoc in state._launching:
                  return func(*args, **kwargs)
              with profile_ctx(engine) as sessions:
                  ret = func(*args, **kwargs)
              state._profiles[(name, engine)] += sessions
              state.param.trigger('_profiles')
              return ret
          return wrapped
      return wrapper
  