def omim(self, omimid=None, hgnc_symbol=None, hgnc_identifier=None, limit=None, as_df=False):
        """Method to query :class:`.models.OMIM` objects in database

        :param omimid: Online Mendelian Inheritance in Man (OMIM) ID(s)
        :type omimid: str or tuple(str) or None

        :param hgnc_symbol: HGNC symbol(s)
        :type hgnc_symbol: str or tuple(str) or None

        :param hgnc_identifier: identifiers(s) in :class:`.models.HGNC`
        :type hgnc_identifier: int or tuple(int) or None

        :param limit:
            - if `isinstance(limit,int)==True` -> limit
            - if `isinstance(limit,tuple)==True` -> format:= tuple(page_number, results_per_page)
            - if limit == None -> all results
        :type limit: int or tuple(int) or None

        :param bool as_df: if `True` results are returned as :class:`pandas.DataFrame`

        :return:
            - if `as_df == False` -> list(:class:`.models.OMIM`)
            - if `as_df == True`  -> :class:`pandas.DataFrame`
        :rtype: list(:class:`.models.OMIM`) or :class:`pandas.DataFrame`

        """
        q = self.session.query(models.OMIM)

        model_queries_config = (
            (omimid, models.OMIM.omimid),
        )
        q = self.get_model_queries(q, model_queries_config)

        one_to_many_queries_config = (
            (hgnc_symbol, models.HGNC.symbol),
            (hgnc_identifier, models.HGNC.identifier)
        )
        q = self.get_one_to_many_queries(q, one_to_many_queries_config)

        return self._limit_and_df(q, limit, as_df)
Method to query :class:`.models.OMIM` objects in database

        :param omimid: Online Mendelian Inheritance in Man (OMIM) ID(s)
        :type omimid: str or tuple(str) or None

        :param hgnc_symbol: HGNC symbol(s)
        :type hgnc_symbol: str or tuple(str) or None

        :param hgnc_identifier: identifiers(s) in :class:`.models.HGNC`
        :type hgnc_identifier: int or tuple(int) or None

        :param limit:
            - if `isinstance(limit,int)==True` -> limit
            - if `isinstance(limit,tuple)==True` -> format:= tuple(page_number, results_per_page)
            - if limit == None -> all results
        :type limit: int or tuple(int) or None

        :param bool as_df: if `True` results are returned as :class:`pandas.DataFrame`

        :return:
            - if `as_df == False` -> list(:class:`.models.OMIM`)
            - if `as_df == True`  -> :class:`pandas.DataFrame`
        :rtype: list(:class:`.models.OMIM`) or :class:`pandas.DataFrame`