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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 datetime_f(dttm):
 """Formats datetime to take less room when it is recent"""

    if dttm:
        dttm = dttm.isoformat()
        now_iso = datetime.now().isoformat()
        if now_iso[:10] == dttm[:10]:
            dttm = dttm[11:]
        elif now_iso[:4] == dttm[:4]:
            dttm = dttm[5:]
    return '<nobr>{}</nobr>'.format(dttm)