'Produce a new :class:`.Session` object using the configuration
established in this :class:`.sessionmaker`.
In Python, the ``__call__`` method is invoked on an object when
it is "called" in the same way as a function::
Session = sessionmaker()
session = Session()  # invokes sessionmaker.__call__()'

def __call__(self, **local_kw):

    for (k, v) in self.kw.items():
        if ((k == 'info') and ('info' in local_kw)):
            d = v.copy()
            d.update(local_kw['info'])
            local_kw['info'] = d
        else:
            local_kw.setdefault(k, v)
    return self.class_(**local_kw)
