parameters: (self, connection, categories, fetch_stream=False)
docstring: Initialize this TracingTrack.
  
      Args:
        connection: a DevToolsConnection.
        categories: ([str] or None) If set, a list of categories to enable or
                    disable in Chrome tracing. Categories prefixed with '-' are
                    disabled.
        fetch_stream: if true, use a websocket stream to fetch tracing data rather
          than dataCollected events. It appears based on very limited testing that
          a stream is slower than the default reporting as dataCollected events.
docstring_summary: Initialize this TracingTrack.
docstring_tokens: Initialize this TracingTrack .
function: def __init__(self, connection, categories, fetch_stream=False):
      """Initialize this TracingTrack.
  
      Args:
        connection: a DevToolsConnection.
        categories: ([str] or None) If set, a list of categories to enable or
                    disable in Chrome tracing. Categories prefixed with '-' are
                    disabled.
        fetch_stream: if true, use a websocket stream to fetch tracing data rather
          than dataCollected events. It appears based on very limited testing that
          a stream is slower than the default reporting as dataCollected events.
      """
      super(TracingTrack, self).__init__(connection)
      if connection:
        connection.RegisterListener('Tracing.dataCollected', self)
  
      self._categories = set(categories)
      params = {}
      params['categories'] = ','.join(self._categories)
      if fetch_stream:
        params['transferMode'] = 'ReturnAsStream'
  
      if connection:
        connection.SyncRequestNoResponse('Tracing.start', params)
  
      self._events = []
      self._base_msec = None
      self._interval_tree = None
      self._main_frame_id = None
function_tokens: def __init__ ( self , connection , categories , fetch_stream = False ) : super ( TracingTrack , self ) . __init__ ( connection ) if connection : connection . RegisterListener ( 'Tracing.dataCollected' , self ) self . _categories = set ( categories ) params = { } params [ 'categories' ] = ',' . join ( self . _categories ) if fetch_stream : params [ 'transferMode' ] = 'ReturnAsStream' if connection : connection . SyncRequestNoResponse ( 'Tracing.start' , params ) self . _events = [ ] self . _base_msec = None self . _interval_tree = None self . _main_frame_id = None