code: def test_attributes():
      A = interface.aslinearoperator(np.arange(16).reshape(4, 4))
  
      def always_four_ones(x):
          x = np.asarray(x)
          assert_(x.shape == (3,) or x.shape == (3, 1))
          return np.ones(4)
  
      B = interface.LinearOperator(
          shape=(4, 3), matvec=always_four_ones
      )
  
      for op in [A, B, A * B, A.H, A + A, B + B, A**4]:
          assert_(hasattr(op, "dtype"))
          assert_(hasattr(op, "shape"))
          assert_(hasattr(op, "_matvec"))
  
imports: from functools import partial
  from itertools import product
  import operator
  import pytest
  from pytest import raises, warns
  from numpy.testing import assert_, assert_equal
  import numpy
  import scipy.sparse
  from scipy.sparse.linalg import interface
  from scipy.sparse.sputils import matrix
label_desc: Use image node_id 3 for calling a global function with example usage: test_attributes() and returns: np