<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def fsliceafter(astr, sub):
 """Return the slice after at sub in string astr"""

    findex = astr.find(sub)
    return astr[findex + len(sub):]