## Not run:
# transform_method <- function(df) cbind_fast(df, q = df$y * df$y)
# data <- data.frame(y = c(1, 2), x = c(0.1, 0.2))
# data_transformed <- transform_method(data)
# process_transform_throw_error(data, data_transformed, "transform_method")
# # transform_method yields data.frame that duplicates input vars - dropping the following
# columns: 'y', 'x'
# # q
# # 1 1
# # 2 4
# ## End(Not run)
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