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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`None` is not correctly serialized for certain optional query params","articleBody":"**Describe the bug**\r\nIn https://github.com/triaxtec/openapi-python-client/pull/331, we decided to allow `None` to be passed in optional query params and treated identically to `UNSET`.\r\n\r\nHowever, a few cases weren't supported:\r\n- model properties\r\n- enum properties\r\n- datetime properties\r\n\r\nI haven't done an exhaustive search so there may be others as well; potentially any types that require non-trivial JSON serialization.\r\n\r\n**To Reproduce**\r\nThis can already be seen in `end_to_end_tests/golden-record/my_test_api_client/api/tests/defaults_tests_defaults_post.py:90`, which will crash if `None` is passed in for the model.\r\n\r\n**Expected behavior**\r\nFor all types, if the query param is optional, `None` is treated as `UNSET`.\r\n\r\n**OpenAPI Spec File**\r\nThe existing `openapi.json`\r\n\r\n**Desktop (please complete the following information):**\r\n - OS: [e.g. macOS 10.15.1]\r\n - Python Version: [e.g. 3.8.0]\r\n - openapi-python-client version [e.g. 0.1.0]\r\n\r\n**Additional context**\r\n","author":{"url":"https://github.com/forest-benchling","@type":"Person","name":"forest-benchling"},"datePublished":"2021-04-07T13:49:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/380/openapi-python-client/issues/380"}