code: def _bytesIO_to_base64(handle_io):
      """Encode the content of a bytesIO virtual file as base64.
  
      Also closes the file.
  
      Returns: data
      """
      handle_io.seek(0)
      data = b64encode(handle_io.read()).decode("utf-8")
      handle_io.close()
      return data
  
imports: import copy
  import json
  import os
  import warnings
  from base64 import b64encode
  from io import BytesIO
  import matplotlib
  import numpy
  from matplotlib.image import imsave
  from nibabel.affines import apply_affine
  from nilearn.plotting.html_document import HTMLDocument
  from .._utils import fill_doc
  from .._utils.extmath import fast_abs_percentile
  from .._utils.niimg import safe_get_data
  from .._utils.niimg_conversions import check_niimg_3d
  from .._utils.param_validation import check_threshold
  from ..datasets import load_mni152_template
  from ..image import get_data, new_img_like, reorder_img, resample_to_img
  from ..plotting import cm
  from ..plotting.find_cuts import find_xyz_cut_coords
  from ..plotting.img_plotting import load_anat
  from .js_plotting_utils import colorscale, get_html_template
label_desc: Use image node_id 4 for calling a global function with example usage: _bytesIO_to_base64(handle_io) and returns: data