Unpack the INFO field into separate fields. E.g.::

        >>> import petl as etl
        >>> # activate bio extensions
        ... import petlx.bio
        >>> table1 = (
        ...     etl
        ...     .fromvcf('fixture/sample.vcf', samples=None)
        ...     .vcfunpackinfo()
        ... )
        >>> table1
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | CHROM | POS     | ID          | REF | ALT    | QUAL | FILTER  | AA   | AC   | AF             | AN   | DB   | DP   | H2   | NS   |
        +=======+=========+=============+=====+========+======+=========+======+======+================+======+======+======+======+======+
        | '19'  |     111 | None        | 'A' | [C]    |  9.6 | None    | None | None | None           | None | None | None | None | None |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '19'  |     112 | None        | 'A' | [G]    |   10 | None    | None | None | None           | None | None | None | None | None |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  |   14370 | 'rs6054257' | 'G' | [A]    |   29 | []      | None | None | [0.5]          | None | True |   14 | True |    3 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  |   17330 | None        | 'T' | [A]    |    3 | ['q10'] | None | None | [0.017]        | None | None |   11 | None |    3 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  | 1110696 | 'rs6040355' | 'A' | [G, T] |   67 | []      | 'T'  | None | [0.333, 0.667] | None | True |   10 | None |    2 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        ...

def vcfunpackinfo(table, *keys):
    """
    Unpack the INFO field into separate fields. E.g.::

        >>> import petl as etl
        >>> # activate bio extensions
        ... import petlx.bio
        >>> table1 = (
        ...     etl
        ...     .fromvcf('fixture/sample.vcf', samples=None)
        ...     .vcfunpackinfo()
        ... )
        >>> table1
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | CHROM | POS     | ID          | REF | ALT    | QUAL | FILTER  | AA   | AC   | AF             | AN   | DB   | DP   | H2   | NS   |
        +=======+=========+=============+=====+========+======+=========+======+======+================+======+======+======+======+======+
        | '19'  |     111 | None        | 'A' | [C]    |  9.6 | None    | None | None | None           | None | None | None | None | None |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '19'  |     112 | None        | 'A' | [G]    |   10 | None    | None | None | None           | None | None | None | None | None |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  |   14370 | 'rs6054257' | 'G' | [A]    |   29 | []      | None | None | [0.5]          | None | True |   14 | True |    3 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  |   17330 | None        | 'T' | [A]    |    3 | ['q10'] | None | None | [0.017]        | None | None |   11 | None |    3 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        | '20'  | 1110696 | 'rs6040355' | 'A' | [G, T] |   67 | []      | 'T'  | None | [0.333, 0.667] | None | True |   10 | None |    2 |
        +-------+---------+-------------+-----+--------+------+---------+------+------+----------------+------+------+------+------+------+
        ...

    """

    result = etl.unpackdict(table, 'INFO', keys=keys)
    return result