def assemble_result_str(ref_snp, alt_snp, flanking_5, flanking_3):
    """
    (str, str, str, str) -> str
    
    ref_snp : str
        DESCRIPTION: 1 character (A, T, G or C), the reference SNP.
    alt_snp : str
        DESCRIPTION: 1 character (A, T, G or C), the variant SNP.
    flanking_5 : str
        DESCRIPTION: 50 characters (A, T, G or C), the 50 bp upstream from ref_snp.
    flanking_3 : str
        DESCRIPTION: 50 characters (A, T, G or C), the 50 bp downstream from ref_snp.
    Returns a new str, the reference SNP concatenated with its variant 
    and its flanking sequences, like this:
        
        ref_snp = 'T'
        alt_snp = 'C'
        50 bp = 'XXXXXXXXXXXXXXX'
        
        'XXXXXXXXXXXXXXX[T/C]XXXXXXXXXXXXXXX'
    """
    return flanking_5 + '[' + ref_snp + '/' + alt_snp + ']' + flanking_3