code: function getcontenttype(obj) {
    if (typeof obj.getHeader === 'function') {
      // res-like
      return obj.getHeader('content-type')
    }
  
    if (typeof obj.headers === 'object') {
      // req-like
      return obj.headers && obj.headers['content-type']
    }
  }
docs: Get content-type from req/res objects.
  
  @param {object}
  @return {Object}
  @private