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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 starting_expression(source_code, offset):
 """Return the expression to complete"""

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