code: def _export_corpus(self):
          
          # bin/mallet import-file --input /Users/erickpeirson/mycorpus_docs.txt
          #     --output mytopic-input.mallet --keep-sequence --remove-stopwords
  
          if not os.path.exists(self.mallet_bin):
              raise IOError("MALLET path invalid or non-existent.")
          self.input_path = os.path.join(self.temp, "input.mallet")
  
          exit = subprocess.call([
                  self.mallet_bin,
                  'import-file',
                  '--input', self.corpus_path,
                  '--output', self.input_path,
                  '--keep-sequence',          # Required for LDA.
                  '--remove-stopwords'])      # Probably redundant.
  
          if exit != 0:
              msg = "MALLET import-file failed with exit code {0}.".format(exit)
              raise RuntimeError(msg)
docs: Calls MALLET's `import-file` method.