feat: extract session variable from referenced testcase step

examples/postman_echo/request_methods/demo_testsuite_yml/request_with_functions_test.py

@@ -10,6 +10,7 @@ class TestCaseRequestWithFunctions(HttpRunner):
         .variables(**{"foo1": "session_bar1", "var1": "testsuite_val1"})
         .base_url("https://postman-echo.com")
         .verify(False)
+        .export(*["session_foo2"])
     )
 
     teststeps = [

examples/postman_echo/request_methods/demo_testsuite_yml/request_with_testcase_reference_test.py

@@ -26,6 +26,23 @@ class TestCaseRequestWithTestcaseReference(HttpRunner):
             RunTestCase("request with functions")
             .with_variables(**{"foo1": "override_bar1"})
             .call(RequestWithFunctions)
+            .extract(*["session_foo2"])
+        ),
+        Step(
+            RunRequest("post form data")
+            .with_variables(**{"foo1": "bar1"})
+            .post("/post")
+            .with_headers(
+                **{
+                    "User-Agent": "HttpRunner/${get_httprunner_version()}",
+                    "Content-Type": "application/x-www-form-urlencoded",
+                }
+            )
+            .with_data("foo1=$foo1&foo2=$session_foo2")
+            .validate()
+            .assert_equal("status_code", 200)
+            .assert_equal("body.form.foo1", "session_bar1")
+            .assert_equal("body.form.foo2", "session_bar2")
         ),
     ]