'Return list of databases matching subject_prefix.'

def GetPrefix(self, subject_prefix):

    components = common.Components(subject_prefix)
    components = [common.ConvertStringToFilename(x) for x in components]
    path_prefix = utils.JoinPath(*components)
    if (path_prefix == '/'):
        path_prefix = ''
    for regex in self.path_regexes:
        result = common.EvaluatePrefix(path_prefix, regex)
        if (result == 'MATCH'):
            (yield self.Get(subject_prefix))
            return
        if (result == 'POSSIBLE'):
            for conn in self.DatabasesByPath(path_prefix):
                (yield conn)
            return
    (yield self.Get(subject_prefix))
