code: def make_mini_img(mini_mesh) -> Callable:
      """Small surface image for tests"""
  
      def f(shape=()):
          data = {}
          for i, (key, val) in enumerate(mini_mesh.items()):
              data_shape = tuple(shape) + (val.n_vertices,)
              data_part = (
                  np.arange(np.prod(data_shape)).reshape(data_shape)
                  + 1.0
              ) * 10**i
              data[key] = data_part
          return SurfaceImage(mini_mesh, data)
  
      return f
  
file_path: nilearn/nilearn/experimental/surface/tests/conftest.py
imports: from typing import Callable
  import numpy
  import pytest
  from nilearn.experimental.surface import InMemoryMesh, PolyMesh, SurfaceImage, load_fsaverage
label_desc: Use image node_id 2 for calling a global function with example usage: make_mini_img(mini_mesh) and returns: f, SurfaceImage