class_docstr: Widget used for display and analysis of image data.
  Implements many features:
  
    * Displays 2D and 3D image data. For 3D data, a z-axis
      slider is displayed allowing the user to select which frame is displayed.
    * Displays histogram of image data with movable region defining the dark/light levels
    * Editable gradient provides a color lookup table
    * Frame slider may also be moved using left/right arrow keys as well as pgup, pgdn, home, and end.
    * Basic analysis features including:
  
        * ROI and embedded plot for measuring image values across frames
        * Image normalization / background subtraction
  
  Basic Usage::
  
      imv = pg.ImageView()
      imv.show()
      imv.setImage(data)
      
  **Keyboard interaction**
  
    * left/right arrows step forward/backward 1 frame when pressed,
      seek at 20fps when held.
    * up/down arrows seek at 100fps
    * pgup/pgdn seek at 1000fps
    * home/end seek immediately to the first/last frame
    * space begins playing frames. If time values (in seconds) are given
      for each frame, then playback is in realtime.
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code: def clear(self):
      self.image = None
      self.imageItem.clear()
  
imports: import os
  from math import log10
  from time import perf_counter
  import numpy
  from ..None import debug
  from ..None import functions
  from ..None import getConfigOption
  from ..graphicsItems.GradientEditorItem import addGradientListToDocstring
  from ..graphicsItems.ImageItem import ImageItem
  from ..graphicsItems.InfiniteLine import InfiniteLine
  from ..graphicsItems.LinearRegionItem import LinearRegionItem
  from ..graphicsItems.ROI import ROI
  from ..graphicsItems.ViewBox import ViewBox
  from ..graphicsItems.VTickGroup import VTickGroup
  from ..Qt import QtCore, QtGui, QtWidgets
  from ..SignalProxy import SignalProxy
  from .None import ImageViewTemplate_generic
label_desc: Use image node_id 3 for calling the ImageView obj's underlying member method code with example usage: obj.clear() without return types