output_directory_onefile = '/Users/jeff/data/cms_npi_specialty_onefile'
npi_filtered.rdd.map(lambda r: r.asDict(True)).coalesce(1).saveAsTextFile(output_directory_onefile)
ls /Users/jeff/data/cms_npi_specialty_onefile
_SUCCESS   part-00000
wc -l /Users/jeff/data/cms_npi_specialty_onefile/part-00000
5031039