Unique constraint using data in multiple tables (SQL / SQLAlchemy)

Question

A top class called Parametric is used to create objects which can have parameters associated with them:

class Parametric(object):
 def __init__(self, name):
  self.name = name
  self.pars = []

class Foo(Parametric):
 def __init__(self, name, prop):
  self.prop = prop
  Parametric.__init__(self, name)

class Bar(Parametric):
 def __init__(self, name, prop):
  self.prop = prop
  Parametric.__init__(self, name)

I use SQLAlchemy for my ORM engine.

I want to impose a UNIQUE constraint that ensures that the combination (name, prop) are unique for a given class (e.g. only one instance of Foo can be called "my_foo" and have a prop value of, say "my_prop"), but I don't see how to reference the name column from Parametric in the Foo table UNIQUECONSTRAINT section.

Is this uniqueness something which can be imposed via FOREIGN KEY directives?