code: def _hstack(X, Y):
      if sp.issparse(X):
          return sp.hstack([X, Y], format=X.format)
      else:
          return np.hstack([X, Y])
  
file_path: scikit-multilearn/skmultilearn/adapt/mltsvm.py
imports: from skmultilearn.base import MLClassifierBase
  import numpy
  import scipy.sparse
  from scipy.linalg import norm
  from scipy.sparse.linalg import inv
  from scipy.linalg import inv
label_desc: Use image node_id 3 for calling a global function with example usage: _hstack(X, Y) and returns: sp, np