I am working on a transform, and adapted this fragment from the example:

case
                when trim(created_time) is NULL
                    then '1970-01-01 00:00:00'
                else
                   CAST(nullif(trim(send_time)), '1970-01-01 00:00:00')
        end as created_time,

But I get the error:

syntax error at or near ")"
  LINE 28:      CAST(nullif(trim(send_time)), '1970-01-01 00:00:00')
                                           ^