add example docs to all datasets and tasks possible

[jhnwu3]

This pull request primarily adds usage examples to the docstrings of dataset and task classes across the codebase, making it easier for users to understand how to instantiate and use these classes. Additionally, there are minor formatting and code cleanup improvements. The most important changes are grouped below:

Documentation improvements (usage examples):

• Added example code snippets to the docstrings of major dataset classes: EHRShotDataset, MIMIC3Dataset, MIMIC4EHRDataset, MIMIC4NoteDataset, MIMIC4CXRDataset, and MIMIC4Dataset to demonstrate typical usage and initialization. [1] [2] [3] [4] [5] [6]
• Added example code snippets to the docstrings of task classes: BenchmarkEHRShot, BMDHSDiseaseClassification, ChestXray14BinaryClassification, ChestXray14MultilabelClassification, COVID19CXRClassification, DrugRecommendationMIMIC4, InHospitalMortalityMIMIC4, LengthOfStayStageNetMIMIC4, and MIMIC3ICD9Coding. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Code formatting and cleanup:

• Improved formatting and consistency in argument lists for dataset class initializers by adding trailing commas. [1] [2] [3] [4]
• Minor code formatting improvements and restructuring for readability in task files, including consistent sample creation and import placement. [1] [2] [3]

Minor functional changes:

• Simplified and clarified logic in the pre_filter method of BenchmarkEHRShot for filtering OMOP tables.

Miscellaneous:

• Added blank lines and improved import organization for clarity in several task files. [1] [2] [3] [4]

These changes collectively enhance usability, readability, and maintainability of the codebase.

[EricSchrock]

Just a couple small items I noticed.

[EricSchrock]

The task currently only supports all lower-case disease names, so the added example will fail. Probably best to update the task to support upper-case too.

        self.disease = disease.lower()
        if self.disease not in ChestXray14Dataset.classes:
            msg = f"Invalid disease: '{self.disease}'! Must be one of {ChestXray14Dataset.classes}."
            logger.error(msg)
            raise ValueError(msg)

[EricSchrock]

I don't think this task uses diagnoses_icd or procedures_icd.

Suggested change

	... tables=["diagnoses_icd", "procedures_icd", "labevents"],
	... tables=["labevents"],

[EricSchrock]

This autoformatting seems a little aggressive. Is this what you're expecting?

Same question throughout this file.