def taxon_database(database, url=None, description=None, id_regex=None):
    """
    Make a taxon database

    :param database: [String] A database name
    :param url: [String] The database URL
    :param description: [String] A description
    :param id_regex: [String] id regex

    :return: A dict

    Usage::

        from pytaxa import constructors as cs
        cs.taxon_database("ncbi", 
            "http://www.ncbi.nlm.nih.gov/taxonomy",
            "NCBI Taxonomy Database", 
            "*")
    """
    return {'database': database, 'url': url, 'description': description,
        'id_regex': id_regex}
