code: def reference_contexts_for_variants(
          variants,
          context_size,
          transcript_id_whitelist=None):
      
      result = OrderedDict()
      for variant in variants:
          result[variant] = reference_contexts_for_variant(
              variant=variant,
              context_size=context_size,
              transcript_id_whitelist=transcript_id_whitelist)
      return result
docs: Extract a set of reference contexts for each variant in the collection.
  
      Parameters
      ----------
      variants : varcode.VariantCollection
  
      context_size : int
          Max of nucleotides to include to the left and right of the variant
          in the context sequence.
  
      transcript_id_whitelist : set, optional
          If given, then only consider transcripts whose IDs are in this set.
  
      Returns a dictionary from variants to lists of ReferenceContext objects,
      sorted by max coding sequence length of any transcript.