input: Write a python function to get Fibonacci series up to n terms.
  assert get_fibonacci_series(5) == [0, 1, 1, 2, 3]
  assert get_fibonacci_series(10) == [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
  assert get_fibonacci_series(1) == [0]
output: def get_fibonacci_series(n):
      if n <= 0:
          return []
      elif n == 1:
          return [0]
      series = [0, 1]
      while len(series) < n:
          series.append(series[-1] + series[-2])
      return series