class_docstr: LuInv:
     helper class to repeatedly solve M*x=b
     using an LU-decomposition of M
class_docstr_tok: ["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 scipy.sparse.linalg.eigen.arpack import _arpack
  import numpy
  from scipy.sparse.linalg.interface import aslinearoperator, LinearOperator
  from scipy.sparse import identity, isspmatrix, isspmatrix_csr
  from scipy.linalg import lu_factor, lu_solve
  from scipy.sparse.sputils import isdense
  from scipy.sparse.linalg import gmres, splu
  import scipy
  import functools
  import operator
  from distutils.version import LooseVersion
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