class_docstr: Extract data from a SurfaceImage.
class_docstr_tok: ["Extract","data","from","a","SurfaceImage","."]
code: def _check_fitted(self):
      if not hasattr(self, "mask_img_"):
          raise ValueError(
              "This masker has not been fitted. Call fit "
              "before calling transform."
          )
  
imports: from __future__ import annotations
  from typing import Any
  import numpy
  import pandas
  from joblib import Memory
  from sklearn.base import BaseEstimator, TransformerMixin
  from nilearn import signal
  from nilearn._utils.cache_mixin import CacheMixin, cache
  from nilearn._utils.class_inspect import get_params
  from nilearn.experimental.surface._surface_image import PolyMesh, SurfaceImage
label_desc: Use image node_id 4 for calling the SurfaceMasker obj's underlying member method code with example usage: obj._check_fitted() without return types