Print Employee Hierarchy as Tree

You are given a list of employee records. Each record is a tuple (employee_name, manager_name) where manager_name is the name of the employee’s direct manager. The CEO has an empty string as manager_name. Build and print the entire employee hierarchy as an indented tree. Each employee must appear on its own line, indented by two spaces for every level it sits below the CEO. Within the same manager, employees must be listed in lexicographic order.