How to use the mongodb-core.ReadPreference function in mongodb-core

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
    }
  }
  return readPreference;
}

Cursor.prototype.setReadPreference = function(r) {
  if(this.s.state != Cursor.INIT) throw MongoError.create({message: 'cannot change cursor readPreference after cursor has been accessed', driver:true});
  if(r instanceof ReadPreference) {
    this.s.options.readPreference = new CoreReadPreference(r.mode, r.tags);
  } else {
    this.s.options.readPreference = new CoreReadPreference(r);
  }

  return this;
}

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags);
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags);
    }
  }
  return readPreference;
}

var getReadPreference = function(self, options, db, coll) {
  var r = null
  if(options.readPreference) {
    r = options.readPreference
  } else if(self.s.readPreference) {
    r = self.s.readPreference
  } else if(db.readPreference) {
    r = db.readPreference;
  }

  if(r instanceof ReadPreference) {
    options.readPreference = new CoreReadPreference(r.mode, r.tags);
  } else if(typeof r == 'string') {
    options.readPreference = new CoreReadPreference(r);
  } else if(r && !(r instanceof ReadPreference) && typeof r == 'object') {
    var mode = r.mode || r.preference;
    if (mode && typeof mode == 'string') {
      options.readPreference = new CoreReadPreference(mode, r.tags);
    }
  }

  return options;
}

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags);
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags);
    }
  }
  return readPreference;
}

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags);
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags);
    }
  }
  return readPreference;
}

if(options.readPreference) {
    r = options.readPreference
  } else if(self.s.readPreference) {
    r = self.s.readPreference
  } else if(db.readPreference) {
    r = db.readPreference;
  }

  if(r instanceof ReadPreference) {
    options.readPreference = new CoreReadPreference(r.mode, r.tags);
  } else if(typeof r == 'string') {
    options.readPreference = new CoreReadPreference(r);
  } else if(r && !(r instanceof ReadPreference) && typeof r == 'object') {
    var mode = r.mode || r.preference;
    if (mode && typeof mode == 'string') {
      options.readPreference = new CoreReadPreference(mode, r.tags);
    }
  }

  return options;
}

var getReadPreference = function(self, options, db, coll) {
  var r = null
  if(options.readPreference) {
    r = options.readPreference
  } else if(self.s.readPreference) {
    r = self.s.readPreference
  } else if(db.readPreference) {
    r = db.readPreference;
  }

  if(r instanceof ReadPreference) {
    options.readPreference = new CoreReadPreference(r.mode, r.tags);
  } else if(typeof r == 'string') {
    options.readPreference = new CoreReadPreference(r);
  }

  return options;
}

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
    }
  }
  return readPreference;
}

var convertReadPreference = function(readPreference) {
  if(readPreference && typeof readPreference == 'string') {
    return new CoreReadPreference(readPreference);
  } else if(readPreference instanceof ReadPreference) {
    return new CoreReadPreference(readPreference.mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
  } else if(readPreference && typeof readPreference == 'object') {
    var mode = readPreference.mode || readPreference.preference;
    if (mode && typeof mode == 'string') {
      readPreference = new CoreReadPreference(mode, readPreference.tags, {maxStalenessSeconds: readPreference.maxStalenessSeconds});
    }
  }
  return readPreference;
}