class_docstr: Camera implementing a MagnifyTransform combined with PanZoomCamera.
  
  Parameters
  ----------
  size_factor : float
      The size factor to use.
  radius_ratio : float
      The radius ratio to use.
  **kwargs : dict
      Keyword arguments to pass to `PanZoomCamera` and create a transform.
  
  Notes
  -----
  This Camera uses the mouse cursor position to set the center position of
  the MagnifyTransform, and uses mouse wheel events to adjust the 
  magnification factor.
  
  At high magnification, very small mouse movements can result in large
  changes, so we use a timer to animate transitions in the transform 
  properties.
  
  The camera also adjusts the size of its "lens" area when the view is
  resized.
code: def view_changed(self):
      # make sure radii are updated when a view is attached.
      # when the view resizes, we change the lens radii to match.
      if self._viewbox is not None:
          vbs = self._viewbox.size
          r = min(vbs) * self.size_factor
          self.mag.radii = r * self.radius_ratio, r
  
      PanZoomCamera.view_changed(self)
  
file_path: vispy/vispy/scene/cameras/magnify.py
imports: from __future__ import division
  import numpy
  from .panzoom import PanZoomCamera
  from ...visuals.transforms.nonlinear import MagnifyTransform, Magnify1DTransform
  from ...app import Timer
label_desc: Use image node_id 7 for calling the MagnifyCamera obj's underlying member method code with example usage: obj.view_changed() without return types