'Return the projection for the given source namespace.'

def projection(self, plain_src_name):

    mapped = self.lookup(plain_src_name)
    if (not mapped):
        return None
    fields = (mapped.include_fields or mapped.exclude_fields)
    if fields:
        include = (1 if mapped.include_fields else 0)
        return dict(((field, include) for field in fields))
    return None
