nloptr.default.options: Description and default values of nloptr options
Description
This data.frame gives shows the options that can be used when solving
  a minimization problem using nloptr. For internal use.Usage
nloptr.default.options
format
ll{
		name							name of the option 
type							type (numeric, logical, integer, character) 
possible_values					string explaining the values the option can take 
default							default value of the option (as a string) 
is_termination_condition		is this option part of the termination conditions? 
description						description of the option (taken from NLopt website if it's an option that is passed on to NLopt). 
}