Queries BioMart.

    :param query_filtery: one BioMart filter associated with the items being queried
    :param query_items: list of items to be queried (must assoiate with given filter)
    :param query_attributes: list of attributes to recover from BioMart
    :param dataset: dataset to query
    :param database: database to query
    :param host: address of the host server, default='www.ensembl.org'

    return: a Pandas dataframe of the queried attributes

def RqueryBM(query_filter,query_items,query_attributes,dataset,database,host=rbiomart_host):
    """
    Queries BioMart.

    :param query_filtery: one BioMart filter associated with the items being queried
    :param query_items: list of items to be queried (must assoiate with given filter)
    :param query_attributes: list of attributes to recover from BioMart
    :param dataset: dataset to query
    :param database: database to query
    :param host: address of the host server, default='www.ensembl.org'

    return: a Pandas dataframe of the queried attributes

    """

    biomaRt = importr("biomaRt")
    ensemblMart=biomaRt.useMart(database, host=rbiomart_host)
    ensembl=biomaRt.useDataset(dataset, mart=ensemblMart)
    df=biomaRt.getBM(attributes=query_attributes, filters=query_filter, values=query_items, mart=ensembl)
    output = [tuple([df[j][i] for j in range(df.ncol)]) for i in range(df.nrow)]
    output = pd.DataFrame(output)
    output.columns = query_attributes
    return output