class_docstr: LuInv:
     helper class to repeatedly solve M*x=b
     using an LU-decomposition of M
code: def _matvec(self, x):
      return lu_solve(self.M_lu, x)
  
imports: from __future__ import division, print_function, absolute_import
  from .None import _arpack
  import numpy
  import warnings
  from scipy.sparse.linalg.interface import aslinearoperator, LinearOperator
  from scipy.sparse import eye, issparse, isspmatrix, isspmatrix_csr
  from scipy.linalg import eig, eigh, lu_factor, lu_solve
  from scipy.sparse.sputils import isdense
  from scipy.sparse.linalg import gmres, splu
  from scipy._lib._util import _aligned_zeros
  from scipy._lib._threadsafety import ReentrancyLock
label_desc: Use image node_id 2 for calling the LuInv obj's underlying member method code with example usage: obj._matvec(x) and returns: lu_solve