Q:

Retain XML version when file is saved in SQL Server database using Python

My Python code pulls locally stored XML file and saves it in a SQL Server database.  However, I see that file stored in database is missing the initial XML version statement:
<? xml version="1.0" encoding="utf-8"? >

In order to retain the initial XML version statement, I came across lxml documentation which states to add parameter xml_declaration=True.  Using this parameter, I can see the XML version printed in python console.  But, when I try to use the same parameter to store it in the database, I get an error:

Type: bytes cannot be serialized exception

Can anyone please help me resolve this exception? 
Python code:
    print("Connecting..")
    # Establish a connection between Python and SQL Server
    conn = pyodbc.connect('Driver={SQL Server};'
                          'Server=TestServer;'
                          'Database=test;'
                          'Trusted_Connection=yes;')
    print("DB Connected..")

    # Open the workbook and define the worksheet
    path = 'C:\\Arelle-master\\arelle\\plugin\\TestPlugin\\TestExcel.xlsx'
    book = xlrd.open_workbook(path)
    print("Excel Loaded into xlrd..")

    # Get XML File
    XMLFilePath = open('C:\\TestPlugin\\HelloWorld.xml')
    x = etree.parse(XMLFilePath)
    print(etree.tostring(x, pretty_print=True, xml_declaration=True)) # Shows correct version of XML file in console. 

    CreateTable = """
    create table test.dbo. StoreInfo
    (
     col1 varchar(100),
     col2 varchar(100),
     col3 varchar(100),
     col4 varchar(100),
     MyXML XML

    )
    """

    # execute create table
    cursor = conn.cursor()
    try:
         cursor.execute(CreateTable)
         conn.commit()
    except pyodbc. ProgrammingError:
        pass
    print("Table Created..")

    InsertQuery = """
    INSERT INTO test.dbo. StoreInfo (
        col1,
        col2,
        col3,
        col4,
        XBRLFile
    ) VALUES (?, ?, ?, ?, ?)""" 

    # Grab existing row count in the database for validation later
    # cursor.execute("SELECT count(*) FROM test.dbo. StoreInfo")
    # before_import = cursor.fetchone()

    for r in range(1, sheet.nrows):
        col1 = sheet.cell(r, 0).value
        col2 = sheet.cell(r, 1).value
        col3 = sheet.cell(r, 2).value
        col4 = sheet.cell(r, 3).value
        col5 = etree.tostring(etree.tostring(x, xml_declaration=True))  # Code throws exception at this line. 

        # Assign values from each row
        values = (col1,col2,col3,col4,col5)

        # Execute SQL Insert Query
        cursor.execute(InsertQuery, values)

Exception:
col5 = etree.tostring(etree.tostring(x, xml_declaration=True))  
File "src\lxml\etree.pyx", line 3391, in lxml.etree.tostring

TypeError: Type 'bytes' cannot be serialized. 

Any idea how to resolve this error? 

A:

MS SQL Server XML data type doesn't preserve XML declaration prolog.  It is stripped out. 
If you do need to have it for any reason you would need to change data type to NVARCHAR(MAX). 
The XML data type is internally stored as UTF-16 encoding.  Even more precise, SQL Server is using varbinary(max) data type
internally, but the content itself is UTF-16 encoded text.