<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_path_from_query_string(req):
 """Gets path from query string Args: req (flask.request):
 Request object from Flask Returns: path (str):
 Value of "path" parameter from query string Raises: exceptions.UserError: If "path" is not found in query string """

    if req.args.get('path') is None:
        raise exceptions.UserError('Path not found in query string')
    return req.args.get('path')