code: def _check_input(self, X):
      if len(X.shape) != 2:
          raise ValueError(
              "Expected 2d matrix, got %s array" % (X.shape,)
          )
  
file_path: fancyimpute/fancyimpute/solver.py
imports: import warnings
  import numpy
  from sklearn.utils import check_array
  from .common import generate_random_column_samples
label_desc: Use image node_id 4 for calling the Solver obj's underlying member method code with example usage: obj._check_input(X) without return types