Ppx_sexp_conv_expander.Attrs
val default : (Ppxlib.label_declaration, Ppxlib.expression) Ppxlib.Attribute.t
val drop_default : (Ppxlib.label_declaration, Ppxlib.expression option) Ppxlib.Attribute.t
val drop_if : (Ppxlib.label_declaration, Ppxlib.expression) Ppxlib.Attribute.t