code: function parseHeaders(headers) {
    var parsed = createMap(), i;
  
    function fillInParsed(key, val) {
      if (key) {
        parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
      }
    }
  
    if (isString(headers)) {
      forEach(headers.split('\n'), function(line) {
        i = line.indexOf(':');
        fillInParsed(lowercase(trim(line.substr(0, i))), trim(line.substr(i + 1)));
      });
    } else if (isObject(headers)) {
      forEach(headers, function(headerVal, headerKey) {
        fillInParsed(lowercase(headerKey), trim(headerVal));
      });
    }
  
    return parsed;
  }
docs: Parse headers into key value object
  
  @param {string} headers Raw headers as a string
  @returns {Object} Parsed headers as key value object