<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def ufo_create_background_layer_for_all_glyphs(ufo_font):
 # type: (defcon.Font) -> None """Create a background layer for all glyphs in ufo_font if not present to reduce roundtrip differences."""


    if "public.background" in ufo_font.layers:
        background = ufo_font.layers["public.background"]
    else:
        background = ufo_font.newLayer("public.background")

    for glyph in ufo_font:
        if glyph.name not in background:
            background.newGlyph(glyph.name)