internal function which returns the gradients of an object of class Rcpp_SEMCpp. This function can be used in optimizers
     
    
    Usage
    .gradientFunction(par, SEM, raw)
 
    
    Arguments
    - par
- labeled vector with parameter values 
- SEM
- model of class Rcpp_SEMCpp. 
- raw
- controls if the internal transformations of lessSEM is used. 
 
    
    Value
    
gradients of the model