old_contents: from __future__ import absolute_import
  
  from .optimization import ParameterManager, minimize
  from .jacobian import FunctionWithApproxJacobian, FunctionWithApproxJacobianCentral
  
new_contents: from __future__ import absolute_import
  
  from .optimization import ParameterManager, minimize
  from .jacobian import FunctionWithApproxJacobian, FunctionWithApproxJacobianCentral
  
  try:
      from .ipopt_wrapper import minimize_ipopt
  except:
      import logging
      logging.error("Could not import ipopt wrapper. Maybe ipopt is not installed?")
  
subject: Make sure package works even if ipopt is not installed