class_docstr: Magnifying lens transform. 
  
  This transform causes a circular region to appear with larger scale around
  its center point. 
  
  Parameters
  ----------
  mag : float
      Magnification factor. Objects around the transform's center point will
      appear scaled by this amount relative to objects outside the circle.
  radii : (float, float)
      Inner and outer radii of the "lens". Objects inside the inner radius
      appear scaled, whereas objects outside the outer radius are unscaled,
      and the scale factor transitions smoothly between the two radii.
  center: (float, float)
      The center (x, y) point of the "lens".
  
  Notes
  -----
  This transform works by segmenting its input coordinates into three
  regions--inner, outer, and transition. Coordinates in the inner region are
  multiplied by a constant scale factor around the center point, and 
  coordinates in the transition region are scaled by a factor that 
  transitions smoothly from the inner radius to the outer radius. 
  
  Smooth functions that are appropriate for the transition region also tend 
  to be difficult to invert analytically, so this transform instead samples
  the function numerically to allow trivial inversion. In OpenGL, the 
  sampling is implemented as a texture holding a lookup table.
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code: def center(self, center):
      if np.allclose(self._center, center):
          return
      self._center = center
      self.shader_map()
      self.shader_imap()
  
imports: from __future__ import division
  import numpy
  from ._util import arg_to_array, arg_to_vec4, as_vec4
  from .base_transform import BaseTransform
  from ...None import gloo
label_desc: Use image node_id 3 for calling the MagnifyTransform obj's underlying member method code with example usage: obj.center(center) without return types