code: def iterate(self):
      if BACKPORT_TO is None:
          return None
      if BACKPORT_TO == "0.10":
          if self.tp in "fd":
              (
                  self.ido,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.info,
              ) = self._arpack_solver(
                  self.ido,
                  self.bmat,
                  self.which,
                  self.k,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.workd,
                  self.workl,
                  self.info,
              )
          else:
              (
                  self.ido,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.info,
              ) = self._arpack_solver(
                  self.ido,
                  self.bmat,
                  self.which,
                  self.k,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.workd,
                  self.workl,
                  self.rwork,
                  self.info,
              )
      elif BACKPORT_TO == "0.09":
          if self.tp in "fd":
              (
                  self.ido,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.info,
              ) = self._arpack_solver(
                  self.ido,
                  self.bmat,
                  self.which,
                  self.k,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.workd,
                  self.workl,
                  self.info,
              )
          else:
              (
                  self.ido,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.info,
              ) = self._arpack_solver(
                  self.ido,
                  self.bmat,
                  self.which,
                  self.k,
                  self.tol,
                  self.resid,
                  self.v,
                  self.iparam,
                  self.ipntr,
                  self.workd,
                  self.workl,
                  self.rwork,
                  self.info,
              )
  
      xslice = slice(self.ipntr[0] - 1, self.ipntr[0] - 1 + self.n)
      yslice = slice(self.ipntr[1] - 1, self.ipntr[1] - 1 + self.n)
      if self.ido == -1:
          # initialization
          self.workd[yslice] = self.OP(self.workd[xslice])
      elif self.ido == 1:
          # compute y = Op*x
          if self.mode in (1, 2):
              self.workd[yslice] = self.OP(self.workd[xslice])
          else:
              Bxslice = slice(
                  self.ipntr[2] - 1, self.ipntr[2] - 1 + self.n
              )
              self.workd[yslice] = self.OPa(self.workd[Bxslice])
      elif self.ido == 2:
          self.workd[yslice] = self.B(self.workd[xslice])
      elif self.ido == 3:
          raise ValueError(
              "ARPACK requested user shifts.  Assure ISHIFT==0"
          )
      else:
          self.converged = True
  
          if self.info == 0:
              pass
          elif self.info == 1:
              self._raise_no_convergence()
          else:
              raise ArpackError(
                  self.info, infodict=self.iterate_infodict
              )
  
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 _UnsymmetricArpackParams obj's underlying member method code with example usage: obj.iterate() and returns: None