input: Write a function to search for a given word in a large document. The function should return the line number of the document where the word is found. If the word is not found, return -1.
  
  assert findWord("This is the first line of the document.\nThis is the second line of the document.\nThis is the third line of the document.", "second") == 2
  assert findWord("This is the first line of the document.\nThis is the second line of the document.\nThis is the third line of the document.", "fourth") == -1
  assert findWord("This is the first line of the document.", "first") == 1
  assert findWord("", "word") == -1
output: def findWord(document, word):
      lines = document.split('\n')
      for i, line in enumerate(lines):
          if word in line:
              return i + 1
      return -1