<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def starting_offset(source_code, offset):
 """Return the offset in which the completion should be inserted Usually code assist proposals should be inserted like:: completion = proposal.name result = (source_code[:starting_offset] + completion + source_code[offset:]) Where starting_offset is the offset returned by this function. """

    word_finder = worder.Worder(source_code, True)
    expression, starting, starting_offset = \
        word_finder.get_splitted_primary_before(offset)
    return starting_offset