input: Write a Python function to convert an integer to its English equivalent.
  assert convert(123) == 'one two three '
  assert convert(0) == 'zero '
  assert convert(4567) == 'four five six seven '
  assert convert(890) == 'eight nine zero '
output: def convert(number):
      num_to_words = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
      result = ""
      for digit in str(number):
          result += num_to_words[int(digit)] + " "
      return result