docstr: Check the type and shape of the data `x`, and coerces it to the correct shape if possible.
  
  Parameters
  ----------
  x
      The data to be checked.
  x_ref
      Whether `x` is a batch of reference data instances (if `True`), or a single test data instance (if `False`).
  
  Returns
  -------
  The checked data, coerced to be a np.ndarray of the correct shape.
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code: def _check_x(self, x: Any, x_ref: bool = False) -> np.ndarray:
      """
      Check the type and shape of the data `x`, and coerces it to the correct shape if possible.
  
      Parameters
      ----------
      x
          The data to be checked.
      x_ref
          Whether `x` is a batch of reference data instances (if `True`), or a single test data instance (if `False`).
  
      Returns
      -------
      The checked data, coerced to be a np.ndarray of the correct shape.
      """
      # Check the type of x
      if isinstance(x, np.ndarray):
          pass
      elif isinstance(x, (int, float)):
          x = np.array([x])
      else:
          raise TypeError(
              "Detectors expect data to be 2D np.ndarray's. If data is passed as another type, a "
              "`preprocess_fn` should be given to convert this data to 2D np.ndarray's."
          )
  
      # Check the shape of x
      if x_ref:
          x = x.reshape(x.shape[0], -1)
      else:
          x = x.reshape(1, -1)
          if x.shape[1] != self.x_ref.shape[1]:
              raise ValueError(
                  "Dimensions do not match. `x` has shape (%d,%d) and `x_ref` has shape (%d,%d)."
                  % (
                      x.shape[0],
                      x.shape[1],
                      self.x_ref.shape[0],
                      self.x_ref.shape[1],
                  )
              )
      return x
  
imports: import logging
  import warnings
  from abc import abstractmethod
  from typing import Any, Callable, Dict, List, Optional, Union, Tuple, TYPE_CHECKING
  import numpy
  from alibi_detect.base import BaseDetector, concept_drift_dict
  from alibi_detect.cd.utils import get_input_shape
  from alibi_detect.utils.state import StateMixin
  from alibi_detect.utils._types import Literal
label_desc: Use image node_id 5 for calling the BaseUniDriftOnline obj's underlying member method code with example usage: obj._check_x(x, x_ref) and returns: x