input: Write a function to compute the average salary from a given CSV file 'salary.csv'. The function should read the file, skip the header, sum up all the salaries, and then return the average.
  
  assert get_average_salary('salary.csv')==2000.0
  assert get_average_salary('empty_salary.csv')==0.0
output: def get_average_salary(filename):
      try:
          with open(filename, 'r') as file:
              lines = file.readlines()[1:]
              total_salary = 0
              count = 0
              for line in lines:
                  salary = float(line.strip())
                  total_salary += salary
                  count += 1
              if count == 0:
                  return 0.0
              return total_salary / count
      except FileNotFoundError:
          return 0.0