flask-sqlalchemy give empty result from database view

Question

I have Model:

from flask.ext.sqlalchemy import SQLAlchemy 
db = SQLAlchemy()
class Graph(db.Model):
    __tablename__ = 'graph_view'
    group = Column(Unicode(250), primary_key=True)
    port_id1 = Column('portid1', Integer)
    port_id2 = Column('portid2', Integer)
    equipment_id1 = Column('equipmentid1', Integer)
    equipment_id2 = Column('equipmentid2', Integer)

where graph_view is database view. I am doing SELECT after connect:

    Graph.query.all()

and i'm getting nothing. Query is not wrong what can i do to fix this?