Flatten Nested HashMap JSON

Given a nested JSON format string, output a flattened string. Assume the JSON object is represented using a nested HashMap where each key maps to either another nested HashMap or a basic type. Design a recursive function to flatten this structure. Input: {"a": 1, "b": {"c": 2, "d": {"e": 3}}} Output: {"a": 1, "b.c": 2, "b.d.e": 3} ```. Please provide multiple test cases to verify the functionality and details on the data scale. Example Input {"a": 1, "b": {"c": 2, "d": {"e": 3}}}