def _get_taxon(tid, taxdump):
    """Get information of a given taxId from taxonomy database.

    Parameters
    ----------
    tid : str
        taxId to query
    taxdump : dict
        taxonomy database

    Returns
    -------
    dict
        information of taxon

    Raises
    ------
    ValueError
        If taxId is not found in taxonomy database.
    """
    try:
        return taxdump[tid]
    except KeyError:
        raise ValueError(f'TaxID {tid} is not found in taxonomy database.')