@Override
    public MapEntryMappers setKeyColumn(String keyColumn) {
        this.keyColumn = keyColumn;
        return this;
    }
Sets the column that map entry keys are loaded from. If set, keys will be loaded from the given column, using the {@link ColumnMapper} registered
for the key type. If unset, keys will be loaded using the {@link RowMapper} registered for the key type, from whichever columns that row mapper
uses.

@param keyColumn the key column name.
@return this config object, for call chaining
core/src/main/java/org/jdbi/v3/core/mapper/MapEntryMappers.java