code: def initial_variant_sequences_from_reads(
          variant_reads,
          max_nucleotides_before_variant=None,
          max_nucleotides_after_variant=None):
      
      unique_sequence_groups = group_unique_sequences(
          variant_reads,
          max_prefix_size=max_nucleotides_before_variant,
          max_suffix_size=max_nucleotides_after_variant)
  
      return [
          VariantSequence(
              prefix=prefix,
              alt=alt,
              suffix=suffix,
              reads=reads)
          for ((prefix, alt, suffix), reads)
          in unique_sequence_groups.items()
      ]
docs: Get all unique sequences from reads spanning a variant locus. This will
      include partial sequences due to reads starting in the middle of the
      sequence around around a variant.