code: def main():
      # Use the same sample data as the waves example, but make it
      # more dependent on y for more interesting contours.
      x, y, z = sample_data((20, 40))
      z = z * -1.5 * y
  
      # Setup a global EckertIII map with faint coastlines.
      fig = plt.figure()
      ax1 = fig.add_subplot(2, 1, 1, projection=ccrs.EckertIII())
      ax1.set_title("transform_first=False")
      ax2 = fig.add_subplot(2, 1, 2, projection=ccrs.EckertIII())
      ax2.set_title("transform_first=True")
  
      for ax, transform_first in zip([ax1, ax2], [False, True]):
          ax.set_global()
          ax.coastlines("110m", alpha=0.1)
  
          # Add colourful filled contours.
          filled_c = ax.contourf(
              x,
              y,
              z,
              transform=ccrs.PlateCarree(),
              transform_first=transform_first,
          )
  
          # And black line contours.
          ax.contour(
              x,
              y,
              z,
              levels=filled_c.levels,
              colors=["black"],
              transform=ccrs.PlateCarree(),
              transform_first=transform_first,
          )
  
      plt.show()
  
imports: import matplotlib.pyplot
  import cartopy.crs
label_desc: Use image node_id 2 for calling a global function with example usage: main() without return types