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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 construct_came_from(environ):
 """ The URL that the user used when the process where interupted for single-sign-on processing. """


    came_from = environ.get("PATH_INFO")
    qstr = environ.get("QUERY_STRING", "")
    if qstr:
        came_from += "?" + qstr
    return came_from