This function will obtain the coefficients (and associated statistics) for each model in the mable.
## S3 method for class 'mdl_df'tidy(x,...)## S3 method for class 'mdl_df'coef(object,...)## S3 method for class 'mdl_ts'tidy(x,...)## S3 method for class 'mdl_ts'coef(object,...)