bug fix and test improvements

[999AICoder]

Reworked imports for pygments MarkdownLexer to remove linter complaints

Reordered expections for two methods based on linter recommendations

Added new test cases to the tests/basic/test_io.py file to cover the add_to_input_history method of the InputOutput class. Specifically:

1 We imported the InMemoryHistory from prompt_toolkit.history to use in our tests.
2 We added two new test methods:
• test_add_to_input_history: This test checks if the method correctly adds input to both the file history and the in-memory history when fancy_input is True.
• test_add_to_input_history_no_prompt_session: This test ensures the method doesn't raise an exception when prompt_session is not initialized (when fancy_input is False).
3 In the aider/io.py file, we updated the add_to_input_history method to use self.prompt_session instead of self.session, fixing a linting issue and making the code consistent with the rest of the class.
4 All 11 tests in test_io.py are now passing, indicating that our changes are working as expected and haven't broken any existing functionality.

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