docstr: Function to concatenate a `numpy` array of strings along a specified axis.
  
  Parameters
  ----------
  arr
      1D `numpy` array of strings.
  dtype
     Array type, used to avoid truncation of strings when concatenating along axis.
  
  Returns
  -------
  Array with one element, the concatenation of the strings in the input array.
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code: def _joiner(
      self, arr: np.ndarray, dtype: Optional[str] = None
  ) -> np.ndarray:
      """
      Function to concatenate a `numpy` array of strings along a specified axis.
  
      Parameters
      ----------
      arr
          1D `numpy` array of strings.
      dtype
         Array type, used to avoid truncation of strings when concatenating along axis.
  
      Returns
      -------
      Array with one element, the concatenation of the strings in the input array.
      """
      if not dtype:
          return np.array(" ".join(arr))
  
      return np.array(" ".join(arr)).astype(dtype)
  
imports: import logging
  from abc import abstractmethod
  from typing import TYPE_CHECKING, Dict, List, Optional, Tuple, Union
  import numpy
  import spacy
label_desc: Use image node_id 3 for calling the AnchorTextSampler obj's underlying member method code with example usage: obj._joiner(arr, dtype) and returns: np, np