input: Write a python function to convert a list of digits into an integer.
  assert convert_to_integer([1, 2, 3, 4]) == 1234
  assert convert_to_integer([0, 6, 7, 8]) == 678
  assert convert_to_integer([5, 0, 3, 2]) == 5032
output: def convert_to_integer(digits):
      return int(''.join(map(str, digits)))