<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def nextSolarReturn(date, lon):
 """ Returns the next date when sun is at longitude 'lon'. """

    jd = eph.nextSolarReturn(date.jd, lon)
    return Datetime.fromJD(jd, date.utcoffset)