Unpack the call column. E.g.::
    
        >>> import petl as etl
        >>> # activate bio extensions
        ... import petlx.bio
        >>> table1 = (
        ...     etl
        ...     .fromvcf('fixture/sample.vcf')
        ...     .vcfmeltsamples()
        ...     .vcfunpackcall()
        ... )
        >>> table1
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | CHROM | POS | ID   | REF | ALT | QUAL | FILTER | INFO | SAMPLE    | DP   | GQ   | GT    | HQ       |
        +=======+=====+======+=====+=====+======+========+======+===========+======+======+=======+==========+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00001' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00002' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00003' | None | None | '0/1' | [3, 3]   |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 112 | None | 'A' | [G] |   10 | None   | {}   | 'NA00001' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 112 | None | 'A' | [G] |   10 | None   | {}   | 'NA00002' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        ...

def vcfunpackcall(table, *keys):
    """
    Unpack the call column. E.g.::
    
        >>> import petl as etl
        >>> # activate bio extensions
        ... import petlx.bio
        >>> table1 = (
        ...     etl
        ...     .fromvcf('fixture/sample.vcf')
        ...     .vcfmeltsamples()
        ...     .vcfunpackcall()
        ... )
        >>> table1
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | CHROM | POS | ID   | REF | ALT | QUAL | FILTER | INFO | SAMPLE    | DP   | GQ   | GT    | HQ       |
        +=======+=====+======+=====+=====+======+========+======+===========+======+======+=======+==========+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00001' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00002' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 111 | None | 'A' | [C] |  9.6 | None   | {}   | 'NA00003' | None | None | '0/1' | [3, 3]   |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 112 | None | 'A' | [G] |   10 | None   | {}   | 'NA00001' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        | '19'  | 112 | None | 'A' | [G] |   10 | None   | {}   | 'NA00002' | None | None | '0|0' | [10, 10] |
        +-------+-----+------+-----+-----+------+--------+------+-----------+------+------+-------+----------+
        ...

    """

    result = (
        etl.wrap(table)
        .convert('CALL', lambda v: v.data._asdict())
        .unpackdict('CALL', keys=keys)
    )
    return result