The function validates the user supplied list of estimation controls and sets
defaults. The defaults follow those set by the respective optimizer. See
maxLik and ucminf for details. Additional options
include `optimizer`, `method`, `cores`, `calculate_hessian` and
`calculate_jacobian`.
set_controls(control)A list of control options
Returns a list of options with missing input values replaced by default values
The function is called once within estimate.