Forum OpenACS Development: create file

I get the following error: ERROR: ProcedureCreate: procedure wp_presentation__get_background already exists with same arguments This is my code see if you can help

    create function wp_presentation__get_background_revision (
    integer ) returns blob as'
    declare
    pres_revision_id        alias for $1;
    v_blob                  blob;  
      begin
        select cr_revisions__content into v_blob
        from cr_revisions ,   
             cr_wp_presentations_background 
        where cr_wp_presentations_background__presentation_id =
    pres_revision_id
        and cr_revisions__revision_id =
    cr_wp_presentations_background__id;
        return v_blob;
      end;' language 'plpgsql';