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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 _parse_connection_string(connstr):
 """ MSSQL style connection string parser Returns normalized dictionary of connection string parameters """

    res = {}
    for item in connstr.split(';'):
        item = item.strip()
        if not item:
            continue
        key, value = item.split('=', 1)
        key = key.strip().lower().replace(' ', '_')
        value = value.strip()
        res[key] = value
    return res