Your task is to simulate and test this complex e$-$learning platform. Implement the following:$$Student Class: Create a Student class that encapsulates the information about students, including usernames, emails, courses, and the get Average Grade$()$ method.$$E$-$Learning Platform Class: Develop a E learning Platform class that manages the collection of students, courses, and grades. Implement thread$-$safe mechanisms to handle concurrent operations, ensuring that students are added without conflicts, courses are distinct, and the mapping of students to the number of courses is accurate.

$$Multi$-$User Simulation: Simulate the e$-$learning platform with multiple threads, reflecting the dynamic nature of students enrolling in various courses concurrently. Consider scenarios where students with similar names or email addresses are added simultaneously, and ensure the platform can handle the complexity of managing diverse student accounts.$$Comprehensive Testing: Design a comprehensive testing scenario that includes various students, courses, and grades. Verify that the e$-$learning platform functions correctly under concurrent operations, students are correctly enrolled in distinct courses, and the mapping of students to the number of courses accurately reflects the dynamic nature of the platform.