docs: def abs2rel_y(y, axis=None):
    r'''
  Transform absolute y-coordinates to relative y-coordinates. Relative coordinates correspond to a
  fraction of the relevant axis. Be sure to set the limits and scale before calling this function!
  
  :arguments:
  
    **y** (``float``, ``list``)
      Absolute coordinates.
  
  :options:
  
    **axis** ([``plt.gca()``] | ...)
      Specify the axis to which to apply the limits.
  
  :returns:
  
    **y** (``float``, ``list``)
      Relative coordinates.
    '''
  
    # get current axis
    if axis is None:
      axis = plt.gca()
  
    # get current limits
    ymin, ymax = axis.get_ylim()
  
    # transform
    # - log scale
    if axis.get_xscale() == 'log':
      try   : return [(np.log10(i)-np.log10(ymin))/(np.log10(ymax)-np.log10(ymin)) if i is not None else i for i in y]
      except: return  (np.log10(y)-np.log10(ymin))/(np.log10(ymax)-np.log10(ymin))
    # - normal scale
    else:
      try   : return [(i-ymin)/(ymax-ymin) if i is not None else i for i in y]
      except: return  (y-ymin)/(ymax-ymin)