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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def group_reads_by_allele(allele_reads):
 """ Returns dictionary mapping each allele's nucleotide sequence to a list of supporting AlleleRead objects. """

    allele_to_reads_dict = defaultdict(list)
    for allele_read in allele_reads:
        allele_to_reads_dict[allele_read.allele].append(allele_read)
    return allele_to_reads_dict