input: Write a function in Python 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.
  
  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 a sample text.\nAnother line here.\nThe word is not present.', 'word')==-1
  assert findWord('This is a test.\nFind me here.\nNo match found.', 'test')==1
  assert findWord('', 'search')==-1
  assert findWord('Single line document with no line break.', 'break')==-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