code: def concatenate(a, b):
      if isinstance(a, csr_matrix) and isinstance(b, csr_matrix):
          return vstack([a, b])
      else:
          return np.concatenate([a, b])
  
file_path: small-text/small_text/utils/labels.py
imports: import numpy
  from scipy.sparse import csr_matrix
  from scipy.sparse import vstack
  from small_text.base import LABEL_UNLABELED
  from small_text.utils.annotations import deprecated
label_desc: Use image node_id 4 for calling a global function with example usage: concatenate(a, b) and returns: vstack, np