Temporarily set parameters on Parameterized object to
    constant=False.

def disable_constant(parameterized):
    """
    Temporarily set parameters on Parameterized object to
    constant=False.
    """
    params = parameterized.params().values()
    constants = [p.constant for p in params]
    for p in params:
        p.constant = False
    try:
        yield
    except:
        raise
    finally:
        for (p, const) in zip(params, constants):
            p.constant = const