def METHOD_NAME():
    """
    Inserts methanisation, feedin and SMR links into the database
    Define the potentials for methanisation and Steam Methane Reaction
    (SMR) modelled as extendable links as well as the H2 feedin
    capacities modelled as non extendable links and insert all of them
    into the database.
    These tree technologies are connecting CH4 and H2_grid buses only.
    The capacity of the H2_feedin links is considerated as constant and
    calculated as the sum of the capacities of the CH4 links connected
    to the CH4 bus multiplied by the H2 energy share allowed to be fed in.
    This share is calculated in the function :py:func:`H2_CH4_mix_energy_fractions`.
    Returns
    -------
    None
    """
    # Connect to local database
    engine = db.engine()
    scn_name = "eGon2035"
    # Select CH4 and corresponding H2 buses
    # No geometry required in this case!
    buses = db.select_dataframe(
        f"""
        SELECT * FROM grid.egon_etrago_ch4_h2 WHERE scn_name = '{scn_name}'
        """
    )
    methanation = buses.copy().rename(
        columns={"bus_H2": "bus0", "bus_CH4": "bus1"}
    )
    SMR = buses.copy().rename(columns={"bus_H2": "bus1", "bus_CH4": "bus0"})
    feed_in = methanation.copy()
    # Delete old entries
    db.execute_sql(
        f"""
            DELETE FROM grid.egon_etrago_link WHERE "carrier" IN
            ('H2_to_CH4', 'H2_feedin', 'CH4_to_H2') AND scn_name = '{scn_name}'
            AND bus0 NOT IN (
               SELECT bus_id FROM grid.egon_etrago_bus
               WHERE scn_name = '{scn_name}' AND country != 'DE'
            ) AND bus1 NOT IN (
               SELECT bus_id FROM grid.egon_etrago_bus
               WHERE scn_name = '{scn_name}' AND country != 'DE'
            );
        """
    )
    scn_params = get_sector_parameters("gas", scn_name)
    pipeline_capacities = db.select_dataframe(
        f"""
        SELECT bus0, bus1, p_nom FROM grid.egon_etrago_link
        WHERE scn_name = '{scn_name}' AND carrier = 'CH4'
        AND (
            bus0 IN (
                SELECT bus_id FROM grid.egon_etrago_bus
                WHERE scn_name = '{scn_name}' AND country = 'DE'
            ) OR bus1 IN (
                SELECT bus_id FROM grid.egon_etrago_bus
                WHERE scn_name = '{scn_name}' AND country = 'DE'
            )
        );
        """
    )
    feed_in["p_nom"] = 0
    feed_in["p_nom_extendable"] = False
    # calculation of H2 energy share via volumetric share outsourced
    # in a mixture of H2 and CH4 with 15 %vol share
    H2_share = scn_params["H2_feedin_volumetric_fraction"]
    H2_energy_share = H2_CH4_mix_energy_fractions(H2_share)
    for bus in feed_in["bus1"].values:
        # calculate the total pipeline capacity connected to a specific bus
        nodal_capacity = pipeline_capacities.loc[
            (pipeline_capacities["bus0"] == bus)
            | (pipeline_capacities["bus1"] == bus),
            "p_nom",
        ].sum()
        # multiply total pipeline capacity with H2 energy share corresponding
        # to volumetric share
        feed_in.loc[feed_in["bus1"] == bus, "p_nom"] = (
            nodal_capacity * H2_energy_share
        )
    # Write new entries
    for table, carrier in zip(
        [methanation, SMR, feed_in], ["H2_to_CH4", "CH4_to_H2", "H2_feedin"]
    ):
        # set parameters according to carrier name
        table["carrier"] = carrier
        table["efficiency"] = scn_params["efficiency"][carrier]
        if carrier != "H2_feedin":
            table["p_nom_extendable"] = True
            table["capital_cost"] = scn_params["capital_cost"][carrier]
            table["lifetime"] = scn_params["lifetime"][carrier]
        new_id = db.next_etrago_id("link")
        table["link_id"] = range(new_id, new_id + len(table))
        table = link_geom_from_buses(table, scn_name)
        table.to_postgis(
            "egon_etrago_link",
            engine,
            schema="grid",
            index=False,
            if_exists="append",
            dtype={"topo": Geometry()},
        )