input: Write a python function to generate a Fibonacci sequence given an initial sequence and sequence length.
  assert generate_fibonacci_sequence([1, 1], 5) == [1, 1, 2, 3, 5]
  assert generate_fibonacci_sequence([1, 1], 7) == [1, 1, 2, 3, 5, 8, 13]
  assert generate_fibonacci_sequence([0, 1], 6) == [0, 1, 1, 2, 3, 5]
output: def generate_fibonacci_sequence(initial_sequence, length):
      sequence = initial_sequence[:]
      while len(sequence) < length:
          sequence.append(sequence[-1] + sequence[-2])
      return sequence