adding helper method to be abel to pass 2D arrays from postgresql to python

src/pg/sql/04_py_agg.sql

@@ -0,0 +1,19 @@
+CREATE OR REPLACE FUNCTION
+    CDB_PyAggS(current_state Numeric[], current_row Numeric[]) 
+    returns NUMERIC[] as $$
+    BEGIN
+        if array_upper(current_state,1) is null  then
+            RAISE NOTICE 'setting state %',array_upper(current_row,1);
+            current_state[1] = array_upper(current_row,1);
+        end if;
+        return array_cat(current_state,current_row) ;
+    END
+    $$ LANGUAGE plpgsql;
+
+
+CREATE AGGREGATE CDB_PyAgg(NUMERIC[])(
+    SFUNC = CDB_PyAggS,
+    STYPE = Numeric[],
+    INITCOND = "{}" 
+);
+