code: def cov(self, amp2, ls, x1, x2=None):
      if x2 is None:
          return amp2 * (
              self.cov_func(ls, x1, None) + 1e-6 * np.eye(x1.shape[0])
          )
      else:
          return amp2 * self.cov_func(ls, x1, x2)
  
imports: import os
  from ..None import gp
  import sys
  from ..None import util
  import tempfile
  import numpy
  import numpy.random
  import scipy.linalg
  import scipy.stats
  import scipy.optimize
  import pickle
  from ..helpers import *
  from ..Locker import *
  import logging
label_desc: Use image node_id 4 for calling the GPEIperSecChooser obj's underlying member method code with example usage: obj.cov(amp2, ls, x1, x2) and returns: unknown, unknown