docstr: We want to handle the case where a split feature is missing. In that case, we go down the
  child that has been the most visited in the past.
docstr_tok: ["We","want","to","handle","the","case","where","a","split","feature","is","missing",".","In","that","case",",","we","go","down","the","child","that","has","been","the","most","visited","in","the","past","."]
code: def next(self, x):
      """
  
      We want to handle the case where a split feature is missing. In that case, we go down the
      child that has been the most visited in the past.
  
      """
      left, right = self.children
      try:
          value = x[self.feature]
      except KeyError:
          if left.l_mass < right.l_mass:
              return right
          return left
      if value < self.threshold:
          return left
      return right
  
imports: from __future__ import annotations
  import collections
  import functools
  import random
  from river import anomaly, base, tree
label_desc: Use image node_id 4 for calling the HSTBranch obj's underlying member method code with example usage: obj.next(x) and returns: right, left, left, right