'For the given name and account client, return an instance of a
L{IGroup<interfaces.IPerson>} provider or create and return a new
instance of a L{IGroup<interfaces.IPerson>} provider.
@type name: C{str}
@param name: The name of the person of interest.
@type client: L{IClient<interfaces.IClient>} provider
@param client: The client account of interest.
@rtype: L{IPerson<interfaces.IPerson>} provider
@return: The person with that C{name}.'

def getPerson(self, name, client):

    account = client.account
    p = self.persons.get((name, account))
    if (not p):
        p = account.getPerson(name)
        self.persons[(name, account)] = p
    return p
