class_docstr: Convert a pyll expression representing a single trial into a pyll
  expression representing multiple trials.
  
  The resulting multi-trial expression is not meant to be evaluated
  directly. It is meant to serve as the input to a suggest algo.
  
  idxs_memo - node in expr graph -> all elements we might need for it
  take_memo - node in expr graph -> all exprs retrieving computed elements
code: def vals_by_label(self):
      return {
          name: self.take_memo[node][0].pos_args[1]
          for name, node in list(self.params.items())
      }
  
imports: import sys
  import numpy
  from .pyll import Apply
  from .pyll import as_apply
  from .pyll import dfs
  from .pyll import toposort
  from .pyll import scope
  from .pyll import stochastic
label_desc: Use image node_id 5 for calling the VectorizeHelper obj's underlying member method code with example usage: obj.vals_by_label() and returns: unknown