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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def render_pdf_file_to_image_files_pdftoppm_pgm(pdf_file_name, root_output_file_path, res_x=150, res_y=150):
 """Same as renderPdfFileToImageFile_pdftoppm_ppm but with -gray option for pgm."""


    comm_output = render_pdf_file_to_image_files_pdftoppm_ppm(pdf_file_name,
                                        root_output_file_path, res_x, res_y, ["-gray"])
    return comm_output