class_docstr: ActivationsProcessor processes a file and returns an Activations instance.
  
  Parameters
  ----------
  mode : {'r', 'w', 'in', 'out', 'load', 'save'}
      Mode of the Processor: read/write.
  fps : float, optional
      Frame rate of the activations (if set, it overwrites the saved frame
      rate).
  sep : str, optional
      Separator between activation values if saved as text file.
  
  Notes
  -----
  An undefined or empty (“”) separator means that the file should be treated
  as a numpy binary file. Only binary files can store the frame rate of the
  activations.
docstr: Add options to save/load activations to an existing parser.
  
  Parameters
  ----------
  parser : argparse parser instance
      Existing argparse parser.
  
  Returns
  -------
  parser_group : argparse argument group
      Input/output argument parser group.
docstr_tok: ["Add","options","to","save\/load","activations","to","an","existing","parser",".","Parameters","--","--","--","--","--","parser",":","argparse","parser","instance","Existing","argparse","parser",".","Returns","--","--","--","-","parser_group",":","argparse","argument","group","Input\/output","argument","parser","group","."]
code: def add_arguments(parser):
      """
      Add options to save/load activations to an existing parser.
  
      Parameters
      ----------
      parser : argparse parser instance
          Existing argparse parser.
  
      Returns
      -------
      parser_group : argparse argument group
          Input/output argument parser group.
  
      """
      # add onset detection related options to the existing parser
      g = parser.add_argument_group("save/load the activations")
      # add options for saving and loading the activations
      g.add_argument(
          "--save",
          action="store_true",
          default=False,
          help="save the activations to file",
      )
      g.add_argument(
          "--load",
          action="store_true",
          default=False,
          help="load the activations from file",
      )
      g.add_argument(
          "--sep",
          action="store",
          default=None,
          help="separator for saving/loading the activations "
          "[default: None, i.e. numpy binary format]",
      )
      # return the argument group so it can be modified if needed
      return g
  
imports: from __future__ import absolute_import, division, print_function
  import numpy
  from ..processors import Processor
  from .None import beats, chords, downbeats, key, notes, onsets, tempo
  from .beats import BeatDetectionProcessor, BeatTrackingProcessor, CRFBeatDetectionProcessor, DBNBeatTrackingProcessor, MultiModelSelectionProcessor, RNNBeatProcessor
  from .chords import CNNChordFeatureProcessor, CRFChordRecognitionProcessor, DeepChromaChordRecognitionProcessor
  from .downbeats import RNNDownBeatProcessor, DBNDownBeatTrackingProcessor, PatternTrackingProcessor, RNNBarProcessor, DBNBarTrackingProcessor
  from .key import CNNKeyRecognitionProcessor
  from .notes import CNNPianoNoteProcessor, ADSRNoteTrackingProcessor, NoteOnsetPeakPickingProcessor, NotePeakPickingProcessor, RNNPianoNoteProcessor
  from .onsets import CNNOnsetProcessor, OnsetPeakPickingProcessor, RNNOnsetProcessor, SpectralOnsetProcessor
  from .tempo import TempoEstimationProcessor
label_desc: Use image node_id 3 for calling the ActivationsProcessor obj's underlying member method code with example usage: obj.add_arguments(parser) and returns: g