For each variant, collect all possible sequence contexts around the
    variant which are spanned by at least min_reads.

    Parameters
    ----------
    variant_and_reads_generator : generator
        Sequence of Variant objects paired with a list of reads which
        overlap that variant.

    min_alt_rna_reads : int
        Minimum number of RNA reads supporting variant allele

    min_variant_sequence_coverage : int
        Minimum number of RNA reads supporting each nucleotide of the
        variant cDNA sequence

    sequence_length : int
        Desired sequence length, including variant nucleotides

    variant_sequence_assembly : bool
        Construct variant sequences by merging overlapping reads. If False
        then variant sequences must be fully spanned by cDNA reads.

    Yields pairs with the following fields:
        - Variant
        - list of VariantSequence objects

def reads_generator_to_sequences_generator(
        variant_and_reads_generator,
        min_alt_rna_reads=MIN_ALT_RNA_READS,
        min_variant_sequence_coverage=MIN_VARIANT_SEQUENCE_COVERAGE,
        preferred_sequence_length=VARIANT_SEQUENCE_LENGTH,
        variant_sequence_assembly=VARIANT_SEQUENCE_ASSEMBLY):
    """
    For each variant, collect all possible sequence contexts around the
    variant which are spanned by at least min_reads.

    Parameters
    ----------
    variant_and_reads_generator : generator
        Sequence of Variant objects paired with a list of reads which
        overlap that variant.

    min_alt_rna_reads : int
        Minimum number of RNA reads supporting variant allele

    min_variant_sequence_coverage : int
        Minimum number of RNA reads supporting each nucleotide of the
        variant cDNA sequence

    sequence_length : int
        Desired sequence length, including variant nucleotides

    variant_sequence_assembly : bool
        Construct variant sequences by merging overlapping reads. If False
        then variant sequences must be fully spanned by cDNA reads.

    Yields pairs with the following fields:
        - Variant
        - list of VariantSequence objects
    """
    for variant, variant_reads in variant_and_reads_generator:
        variant_sequences = reads_to_variant_sequences(
            variant=variant,
            reads=variant_reads,
            min_alt_rna_reads=min_alt_rna_reads,
            min_variant_sequence_coverage=min_variant_sequence_coverage,
            preferred_sequence_length=preferred_sequence_length,
            variant_sequence_assembly=variant_sequence_assembly)
        yield variant, variant_sequences