SqlAlchemy中的“不规则”SQL函数

在SqlAlchemy ORM中,我如何使用需要关键字和参数的SQL函数,例如, POSITION(substr IN str) 。以下操作无效:

from sqlalchemy import Column, Integer, String, select
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class SomeClass(Base):
    __tablename__ = 'a'
    id = Column(Integer, primary_key=True)
    name =  Column(String(50))



sel = select(SomeClass).where( POSITION('x' IN name) > 5 ) # doesn't work