Save customized function inside function in MLFlow log_model - r

Question

I would like to do something with MLFlow but I do not find any solution on Internet. I am working with MLFlow and R, and I want to save a regression model. The thing is that by the time I want to predict the testing data, I want to do some transformation of that data. Then I have:
data <- #some data with numeric regressors and dependent variable called 'y'
# Divide into train and test
ind <- sample(nrow(data), 0.8*nrow(data), replace = FALSE)
dataTrain <- data[ind,]
dataTest <- data[-ind,]
# Run model in the mlflow framework
with(mlflow_start_run(), {
model <- lm(y ~ ., data = dataTrain)
predict_fun <- function(model, data_to_predict){
data_to_predict[,3] <- data_to_predict[,3]/2
data_to_predict[,4] <- data_to_predict[,4] + 1
return(predict(model, data_to_predict))
}
predictor <- crate(~predict_fun(model,dataTest),model)
### Some code to use the predictor to get the predictions and measure the accuracy as a log_metric
##################
##################
##################
mlflow_log_model(predictor,'model')
}
As you can notice, my prediction function not only consists in predict the new data you are evaluating, but it also makes some transformations in the third and fourth columns. All examples I saw on the web use the function predict in the crate as the default function of R.
Once I save this model, when I run it in another notebook with some Test data, I get the error: "predict_fun" doesn't exist. That is because my algorithm has not saved this specific function. Do you know what can I do to save and specific prediction function that I have created instead of the default functions that are in R?
This is not the real example I am working with, but it is an approximation of it. The fact is that I want to save extra functions apart from the model itself.
Thank you very much!