- dbt_utils.not_null_proportion: 
      at_least: 0.95
      group_by_columns: [date_trunc('week', timestamp)]

select
      count(*) as failures,
      count(*) != 0 as should_warn,
      count(*) != 0 as should_error
    from (
 
with validation as (
  select
    date_trunc('week' ,timestamp), 
    sum(case when visit_reasons is null then 0 else 1 end) / cast(count(*) as numeric) as not_null_proportion
  from <my_table>
  group by date_trunc('week',timestamp)
),
validation_errors as (
  select
    date_trunc('week' ,timestamp), 
    not_null_proportion
  from validation
  where not_null_proportion < 0.95 or not_null_proportion > 1
)
select
  *
from validation_errors
    ) dbt_internal_test

with validation as (
  select
    {% for c in select_gb_cols %}
    {{select_gb_cols}} as group_col_{{loop.counter}}{% if not loop.last %},{%endif%}
    {% endear %}
    sum(case when {{ column_name }} is null then 0 else 1 end) / cast(count(*) as {{ dbt.type_numeric() }}) as not_null_proportion
  from {{ model }}
  {{groupby_gb_cols}}
),
validation_errors as (
  select
   {% for c in select_gb_cols %}
    group_col_{{loop.counter}}{% if not loop.last %},{%endif%}
    {% endear %}
    not_null_proportion
  from validation
  where not_null_proportion < {{ at_least }} or not_null_proportion > {{ at_most }}