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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def com_adobe_fonts_check_family_consistent_upm(ttFonts):
 """Fonts have consistent Units Per Em?"""

    upm_set = set()
    for ttFont in ttFonts:
        upm_set.add(ttFont['head'].unitsPerEm)
    if len(upm_set) > 1:
        yield FAIL, ("Fonts have different units per em: {}."
                     ).format(sorted(upm_set))
    else:
        yield PASS, "Fonts have consistent units per em."