code: def _find_midpoints(self, lim, ticks):
      # Find the center point between each lat gridline.
      if len(ticks) > 1:
          cent = np.diff(ticks).mean() / 2
      else:
          cent = np.nan
      if isinstance(self.axes.projection, _POLAR_PROJS):
          lq = 90
          uq = 90
      else:
          lq = 25
          uq = 75
      midpoints = (
          self._round(np.percentile(lim, lq), cent),
          self._round(np.percentile(lim, uq), cent),
      )
      return midpoints
  
imports: import itertools
  import operator
  import warnings
  import matplotlib
  import matplotlib.artist
  import matplotlib.collections
  import matplotlib.text
  import matplotlib.ticker
  import matplotlib.transforms
  import numpy
  import shapely.geometry
  import cartopy
  from cartopy.crs import PlateCarree, Projection, _RectangularProjection
  from cartopy.mpl.ticker import LatitudeFormatter, LatitudeLocator, LongitudeFormatter, LongitudeLocator
label_desc: Use image node_id 15 for calling the Gridliner obj's underlying member method code with example usage: obj._find_midpoints(lim, ticks) and returns: midpoints