_convert = function( srcs, dst, opts ) {

  // If no source resumes are specified, error out
  let fmtUp;
  if (!srcs || !srcs.length) {
    this.err(HMSTATUS.resumeNotFound, { quit: true });
    return null;
  }

  // If no destination resumes are specified, error out except for the special
  // case of two resumes:
  //   hackmyresume CONVERT r1.json r2.json
  if (!dst || !dst.length) {
    if (srcs.length === 1) {
      this.err(HMSTATUS.inputOutputParity, { quit: true });
    } else if (srcs.length === 2) {
      dst = dst || []; dst.push( srcs.pop() );
    } else {
      this.err(HMSTATUS.inputOutputParity, { quit: true });
    }
  }

  // Different number of source and dest resumes? Error out.
  if (srcs && dst && srcs.length && dst.length && (srcs.length !== dst.length)) {
    this.err(HMSTATUS.inputOutputParity, { quit: true });
  }

  // Validate the destination format (if specified)
  //const targetVer = null;
  if (opts.format) {
    fmtUp = opts.format.trim().toUpperCase();
    if (!_.contains(['FRESH','FRESCA','JRS','JRS@1','JRS@edge'], fmtUp)) {
      this.err(HMSTATUS.invalidSchemaVersion, {data: opts.format.trim(), quit: true});
    }
  }
    // freshVerRegex = require '../utils/fresh-version-regex'
    // matches = fmtUp.match freshVerRegex()
    // # null
    // # [ 'JRS@1.0', 'JRS', '1.0', index: 0, input: 'FRESH' ]
    // # [ 'FRESH', 'FRESH', undefined, index: 0, input: 'FRESH' ]
    // if not matches
    //   @err HMSTATUS.invalidSchemaVersion, data: opts.format.trim(), quit: true
    // targetSchema = matches[1]
    // targetVer = matches[2] || '1'

  // If any errors have occurred this early, we're done.
  if (this.hasError()) {
    this.reject(this.errorCode);
    return null;
  }

  // Map each source resume to the converted destination resume
  const results = _.map(srcs, function( src, idx ) {

    // Convert each resume in turn
    const r = _convertOne.call(this, src, dst, idx, fmtUp);

    // Handle conversion errors
    if (r.fluenterror) {
      r.quit = opts.assert;
      this.err(r.fluenterror, r);
    }
    return r;
  }
  , this);


  if (this.hasError() && !opts.assert) {
    this.reject(results);
  } else if (!this.hasError()) {
    this.resolve(results);
  }
  return results;
}
Private workhorse method. Convert 0..N resumes between FRESH and JRS
formats.