input: Write a function to output the Fibonacci sequence as a list of integers in Python up to the nth term. The function should be called `fibonacci_sequence` and take an integer `n` as input. The output should be a list containing the first `n` Fibonacci numbers. If `n` is less than or equal to 0, the function should return an empty list.
  
  assert fibonacci_sequence(5)==[0, 1, 1, 2, 3]
  assert fibonacci_sequence(10)==[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
  assert fibonacci_sequence(1)==[0]
  assert fibonacci_sequence(0)==[]
  assert fibonacci_sequence(-3)==[]
output: if n <= 0:
      return []
  elif n == 1:
      return [0]
  elif n == 2:
      return [0, 1]
  else:
      fib_seq = [0, 1]
      for i in range(2, n):
          fib_seq.append(fib_seq[-1] + fib_seq[-2])
      return fib_seq