Connection to tables using PLACEHOLDERs

**Is your feature request related to a problem? Please describe.** Several tables at my work require the use of PLACEHOLDER syntax, like: ```sql FROM "_SYS_BIC"."NAME_SPACE/TABLE_NAME"( 'PLACEHOLDER' = ('$$Calweek_ISO_From$$', '2025-01-01'), 'PLACEHOLDER' = ('$$Calweek_ISO_To$$', '9999-01-01'), 'PLACEHOLDER' = ('$$Active_or_Historical$$', 'A') ) ``` I'd like to have that table represented in SQLAlchemy, but the docs don't mention how to instantiate a table with PLACEHOLDER syntax. I don't see anything in the issues either. I feel that there should be a section in the docs for the PLACEHOLDER syntax. That said, thanks so much for the work on the sqlalchemy integration. It is helping a lot in our data pipelines.