class documentation
        
        
        container to keep track of the best solution seen.
Keeps also track of the genotype, if available.
| Method | __init__ | initialize the best solution with x, f, and evals. | 
| Method | get | return (x, f, evals) | 
| Method | update | checks for better solutions in list arx. | 
| Instance Variable | compared | number of overall compared values, posterior hack | 
| Instance Variable | evals | Undocumented | 
| Instance Variable | evalsall | Undocumented | 
| Instance Variable | f | Undocumented | 
| Instance Variable | last | Undocumented | 
| Instance Variable | x | Undocumented | 
| Instance Variable | x | Undocumented | 
checks for better solutions in list arx.
Based on the smallest corresponding value in arf,
alternatively, update may be called with a BestSolution
instance like update(another_best_solution) in which case
the better solution becomes the current best.
xarchive is used to retrieve the genotype of a solution.