'Retrieve information about the namespaces available to this account
This command is allowed in the Authenticated and Selected states.
@rtype: C{Deferred}
@return: A deferred whose callback is invoked with namespace
information.  An example of this information is::
which indicates a single personal namespace called \'\' with \'/\'
as its hierarchical delimiter, and no shared or user namespaces.'

def namespace(self):

    cmd = 'NAMESPACE'
    resp = ('NAMESPACE',)
    d = self.sendCommand(Command(cmd, wantResponse=resp))
    d.addCallback(self.__cbNamespace)
    return d
