Applies the supplied transformer function to code chunks identified within an Rmd or Rnw file and recombines the resulting (styled) code chunks with the text chunks.
transform_mixed(lines, transformer_fun, filetype)
A character vector of lines from an Rmd or Rnw file.
A styler transformer function.
A string indicating the filetype - either 'Rmd' or 'Rnw'.