def to_sorted_escaped_s
      creds.sort_by { |cred, _| cred }
           .map { |cred, value| "#{escaped(cred.to_s)}:#{escaped(value)}" }
           .join(',')
    end
def to_sorted_escaped_s
      creds.sort_by { |cred, _| cred }
           .map { |cred, value| "#{escaped(cred.to_s)}:#{escaped(value)}" }
           .join(',')
    end
Initializes a credentials object from a 'creds' hash.
 The accepted fields of the hash are:
   app_id, app_key, referrer, user_id, user_key, and access_token.
 Extra fields are discarded.
 This method returns all the credentials with this format:
 credential1:value1,credential2:value2, etc.
 The delimiters used, ',' and ':', are escaped in the values. Also, the
 credentials appear in alphabetical order.