docstr: get extreme values.
  
  x1, y1, x2, y2 in image coordinates (0-based)
  nx, ny : number of division in each axis
docstr_tok: ["get","extreme","values",".","x1",",","y1",",","x2",",","y2","in","image","coordinates","(","0-based",")","nx",",","ny",":","number","of","division","in","each","axis"]
code: def __call__(self, transform_xy, x1, y1, x2, y2):
      """
      get extreme values.
  
      x1, y1, x2, y2 in image coordinates (0-based)
      nx, ny : number of division in each axis
      """
      x_, y_ = np.linspace(x1, x2, self.nx), np.linspace(
          y1, y2, self.ny
      )
      x, y = np.meshgrid(x_, y_)
      lon, lat = transform_xy(np.ravel(x), np.ravel(y))
  
      lon_min, lon_max = lon.min(), lon.max()
      lat_min, lat_max = lat.min(), lat.max()
  
      return self._add_pad(lon_min, lon_max, lat_min, lat_max)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import numpy
  from matplotlib.transforms import Bbox
  from .None import clip_path
  import matplotlib.ticker
  from matplotlib.transforms import Transform
label_desc: Use image node_id 2 for calling the ExtremeFinderSimple obj's underlying member method code with example usage: obj.__call__(transform_xy, x1, y1, x2, y2) and returns: self