sqlalchemy : executing raw sql with parameter bindings

You need to get the connection object, call execute() on it and pass query parameters as keyword arguments:

from alembic import op
from sqlalchemy.sql import text

conn = op.get_bind()
conn.execute(
    text(
        """
            insert into field_tags 
            (id, field_id, code, description) 
            values 
            (1, 'zasz', :code , :description)
        """
    ), 
    **t
)

Also see: How to execute raw SQL in SQLAlchemy-flask app.