Returns a list of entities for this blob.

def entities(self):
    """Returns a list of entities for this blob."""
    start = 0
    end = 0
    prev_tag = u'O'
    chunks = []
    for i, (w, tag) in enumerate(self.ne_chunker.annotate(self.words)):
      if tag != prev_tag:
        if prev_tag == u'O':
          start = i
        else:
          chunks.append(Chunk(self.words[start: i], start, i, tag=prev_tag,
                              parent=self))
        prev_tag = tag
    if tag != u'O':
      chunks.append(Chunk(self.words[start: i+1], start, i+1, tag=tag,
                          parent=self))
    return chunks