retrieving object based on its URI using RDFAlchemy and rdflib

Question

I am using RDFAlchemy and rdflib graph for the source of the data, i.e. rdfalchemy.rdfSubject.db. How can I have rdfalchemy map an object if I have its uri? calling the constructor with the uri creates an object but doesn't retrieve values of other properties from the graph. Using get_by(resUri='http://...') yields an AttributeError

class Book(rdfAlchemy.rdfSubject):
  rdf_type = BIBO.Book
  isbn = rdfalchemy.rdfSingle(BIBO.isbn10)
Book.get_by(resUri='') # AttributeError
b = Book(uri) #a book identified with uri exists in the data 
b.title #empty string

Answer 1

I guess should be something like:

b = Book(URIRef(uri))