class_docstr: Transforms the input sentence by removing a subordinate clause.
  
  Example::
  
      original: "The bill intends to restrict the RTC to
          Treasury borrowings only, unless the agency receives
          specific congressional authorization."
      transformed: "The bill intends to restrict the RTC to
          Treasury borrowings only."
docstr: Find all the subtrees that can be removed.
  
  :param ~DPSample sample:
  :return: A list of the subtrees, long to short.
docstr_tok: ["Find","all","the","subtrees","that","can","be","removed",".",":","param","~DPSample","sample",":",":","return",":","A","list","of","the","subtrees",",","long","to","short","."]
code: def find_subtree(self, sample):
      r"""
      Find all the subtrees that can be removed.
  
      :param ~DPSample sample:
      :return: A list of the subtrees, long to short.
  
      """
      words = sample.get_words("x")
      heads = sample.get_value("head")
      punc = []
      subtrees = []
  
      for i, word in enumerate(words):
          if word in (",", "."):
              punc.append(i + 1)
      if len(punc) == 1:
          return None
  
      for i in range(len(punc) - 1):
          start = punc[i]
          end = punc[i + 1]
          flag = True
          bracket = 0
          interval = list(range(start + 1, end))
  
          for j, head in enumerate(heads):
              if int(head) in interval and (j + 1) not in interval:
                  flag = False
                  break
  
          for word in words[start : end - 1]:
              if word in ("-LRB-", "-RRB-"):
                  bracket += 1
          if flag is True and bracket % 2 == 0:
              subtrees.append((start, end))
  
      return sorted(subtrees, key=self.get_difference, reverse=True)
  
imports: from ..transformation import Transformation
label_desc: Use image node_id 3 for calling the DeleteSubTree obj's underlying member method code with example usage: obj.find_subtree(sample) and returns: sorted, None