<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def addAccount(self, siteStore, username, domain, password):
 """ Create a new account in the given store. @param siteStore: A site Store to which login credentials will be added. @param username: Local part of the username for the credentials to add. @param domain: Domain part of the username for the credentials to add. @param password: Password for the credentials to add. @rtype: L{LoginAccount} @return: The added account. """

        for ls in siteStore.query(userbase.LoginSystem):
            break
        else:
            ls = self.installOn(siteStore)
        try:
            acc = ls.addAccount(username, domain, password)
        except userbase.DuplicateUser:
            raise usage.UsageError("An account by that name already exists.")
        return acc