code: def _trace(A):
      # A compatibility function which should eventually disappear.
      if is_pydata_spmatrix(A):
          return A.to_scipy_sparse().trace()
      else:
          return A.trace()
  
imports: from warnings import warn
  import numpy
  import scipy.linalg
  import scipy.sparse.linalg
  from scipy.linalg._decomp_qr import qr
  from scipy.sparse._sputils import is_pydata_spmatrix
  from scipy.sparse.linalg import aslinearoperator
  from scipy.sparse.linalg._interface import IdentityOperator
  from scipy.sparse.linalg._onenormest import onenormest
label_desc: Use image node_id 3 for calling a global function with example usage: _trace(A) and returns: A, A