I only just noticed you are using DLT. My bad.

The @Dlt.table decorator tells DLT to create a table that contains the result of a DataFrame. 

Basically, you can't operate on the result of the function as you're used to operating on a DataFrame, but you need to operate on the DLT table it created, using dlt.read(<table_name>). If you want to do DataFrame operations on the table you've created, you need to use dlt.read(<table_name>).count()

Example:

@Dlt.table
def test():
  if dlt.read("today_latest_execution").count() >= 0:
    return dlt.read("today_latest_execution")

DLT works a lot differently than what you're used to with working with function return values.

Hope this helps! 

Edit: argh, somehow my post keeps tagging user Dlt haha but I think you get the point!