How to save an xml string in a document?

I want to save my xml which is an STR (return from an API) in a file .xml, but when I do it does not fuciona someone could help me?

from xml.dom import minidom
cont = minidom.parseString(xml)
arquivo = open(local_save, 'wb')
cont.writexml(arquivo)
arquivo.close()

The function I'm using would be this: All values in it are str, and I want to convert that str to a document .xml

def salvarXML(self, xml, caminho, chNFe, tpEvento, nSeqEvento):
    local_save = caminho + tpEvento + chNFe + nSeqEvento + '-NFe.xml'
    cont = minidom.parseString(xml)
    arquivo = open(local_save, 'wb')
    cont.writexml(arquivo)
    arquivo.close()

The xml that is as string:

 ?xml version="1.0" encoding="utf-8"?>
<NFe>
    <infNFe versao="4.00" Id="NFe43181107364617000135550000000048051004621865">
        <ide>
            <cUF>43</cUF>
            <cNF>00462186</cNF>
            <natOp>VENDA A PRAZO - S</natOp>
            <mod>55</mod>
            <serie>0</serie>
            <nNF>4805</nNF>
            <dhEmi>2018-11-05T09:55:59-02:00</dhEmi>
            <tpNF>1</tpNF>
            <idDest>1</idDest>
            <cMunFG>4305108</cMunFG>
            <tpImp>1</tpImp>
            <tpEmis>1</tpEmis>
            <cDV>5</cDV>
            <tpAmb>2</tpAmb>
            <finNFe>1</finNFe>
            <indFinal>0</indFinal>
            <indPres>9</indPres>
            <procEmi>0</procEmi>
            <verProc>4.00|NS_API</verProc>
        </ide>
        <emit>
            <CNPJ>00000000000000</CNPJ>
            <xNome>Teste de Acentos: áéíóâêãõàèìò �?É�?ÓÂÊÃÕÀÈÌÒ</xNome>
            <enderEmit>
                <xLgr>Rua Bento Osvaldo Trisch</xLgr>
                <nro>.</nro>
                <xCpl></xCpl>
                <xBairro>Pendancino</xBairro>
                <cMun>4303509</cMun>
                <xMun>Caxias do Sul</xMun>
                <UF>RS</UF>
                <CEP>95046600</CEP>
                <fone>0000000000</fone>
            </enderEmit>
            <IE>0000000000</IE>
            <CRT>3</CRT>
        </emit>
        <dest>
            <CNPJ>00000000000000</CNPJ>
            <xNome>NF-E EMITIDA EM AMBIENTE DE HOMOLOGACAO - SEM VALOR FISCAL</xNome>
            <enderDest>
                <xLgr>AV ANTONIO DURO</xLgr>
                <nro>0</nro>
                <xBairro>OLARIA</xBairro>
                <cMun>4303509</cMun>
                <xMun>CAMAQUA</xMun>
                <UF>RS</UF>
                <CEP>96180000</CEP>
                <cPais>1058</cPais>
                <xPais>BRASIL</xPais>
            </enderDest>
            <indIEDest>1</indIEDest>
            <IE>0000000000</IE>
            <email>[email protected]</email>
        </dest>
        <det nItem="1">
            <prod>
                <cProd>1440859X1_</cProd>
                <cEAN>SEM GTIN</cEAN>
                <xProd>Teste de Acentos: áéíóâêãõàèìò �?É�?ÓÂÊÃÕÀÈÌÒ</xProd>
                <NCM>87089990</NCM>
                <CEST>0107500</CEST>
                <CFOP>5101</CFOP>
                <uCom>UN</uCom>
                <qCom>1.0000</qCom>
                <vUnCom>250.0000</vUnCom>
                <vProd>250.00</vProd>
                <cEANTrib>SEM GTIN</cEANTrib>
                <uTrib>UN</uTrib>
                <qTrib>1.0000</qTrib>
                <vUnTrib>250.0000</vUnTrib>
                <indTot>1</indTot>
                <nItemPed>0</nItemPed>
            </prod>
            <imposto>
                <vTotTrib>50.00</vTotTrib>
                <ICMS>
                    <ICMS10>
                        <orig>0</orig>
                        <CST>10</CST>
                        <modBC>0</modBC>
                        <vBC>250.00</vBC>
                        <pICMS>18.00</pICMS>
                        <vICMS>45.00</vICMS>
                        <vBCFCP>250.00</vBCFCP>
                        <pFCP>2.00</pFCP>
                        <vFCP>5.00</vFCP>
                        <modBCST>4</modBCST>
                        <pMVAST>32.00</pMVAST>
                        <pRedBCST>0.00</pRedBCST>
                        <vBCST>330.00</vBCST>
                        <pICMSST>18.00</pICMSST>
                        <vICMSST>14.40</vICMSST>
                        <vBCFCPST>330.00</vBCFCPST>
                        <pFCPST>2.00</pFCPST>
                        <vFCPST>1.60</vFCPST>
                    </ICMS10>
                </ICMS>
                <IPI>
                    <cEnq>999</cEnq>
                    <IPINT>
                        <CST>53</CST>
                    </IPINT>
                </IPI>
                <PIS>
                    <PISAliq>
                        <CST>01</CST>
                        <vBC>250.00</vBC>
                        <pPIS>1.65</pPIS>
                        <vPIS>4.12</vPIS>
                    </PISAliq>
                </PIS>
                <COFINS>
                    <COFINSAliq>
                        <CST>01</CST>
                        <vBC>250.00</vBC>
                        <pCOFINS>7.60</pCOFINS>
                        <vCOFINS>19.00</vCOFINS>
                    </COFINSAliq>
                </COFINS>
            </imposto>
        </det>
        <total>
            <ICMSTot>
                <vBC>250.00</vBC>
                <vICMS>45.00</vICMS>
                <vICMSDeson>0.00</vICMSDeson>
                <vFCPUFDest>0.00</vFCPUFDest>
                <vICMSUFDest>0.00</vICMSUFDest>
                <vICMSUFRemet>0.00</vICMSUFRemet>
                <vFCP>5.00</vFCP>
                <vBCST>330.00</vBCST>
                <vST>14.40</vST>
                <vFCPST>1.60</vFCPST>
                <vFCPSTRet>0.00</vFCPSTRet>
                <vProd>250.00</vProd>
                <vFrete>0.00</vFrete>
                <vSeg>0.00</vSeg>
                <vDesc>0.00</vDesc>
                <vII>0.00</vII>
                <vIPI>0.00</vIPI>
                <vIPIDevol>0.00</vIPIDevol>
                <vPIS>4.12</vPIS>
                <vCOFINS>19.00</vCOFINS>
                <vOutro>0.00</vOutro>
                <vNF>266.00</vNF>
                <vTotTrib>50.00</vTotTrib>
            </ICMSTot>
        </total>
        <transp>
            <modFrete>1</modFrete>
            <transporta>
                <CNPJ>0000000000000</CNPJ>
                <xNome>EL TESTE</xNome>
                <IE>0000000000</IE>
                <xEnder>ESTR BENTO OSVALDO TRISCH</xEnder>
                <xMun>CAXIAS DO SUL</xMun>
                <UF>RS</UF>
            </transporta>
            <veicTransp>
                <placa>ABC1234</placa>
                <UF>RS</UF>
                <RNTC>12345678</RNTC>
            </veicTransp>
            <vol>
                <qVol>0</qVol>
                <marca>TESTE</marca>
                <nVol>0</nVol>
                <pesoL>0.000</pesoL>
                <pesoB>0.000</pesoB>
            </vol>
        </transp>
        <pag>
            <detPag>
                <tPag>15</tPag>
                <vPag>266.00</vPag>
            </detPag>
            <vTroco>0.00</vTroco>
        </pag>
        <infAdic>
            <infCpl>Teste de Acentos: áéíóâêãõàèìò �?É�?ÓÂÊÃÕÀÈÌÒ DESCONTO PIS 0,01 COFINS 0,06 LEI 11.196 DE 21/11/2005</infCpl>
        </infAdic>
    </infNFe>
</NFe>

I get this xml through this code that calls my function saves xml:

    if(tpDown.upper().count('X') == 1):
        xml = resposta['xml']
        self.salvarXML(self, xml, caminho, chNFe, '', '')

Json returned by API:

{'status': 200, 'motivo': 'Consulta realizada com sucesso', 'chNFe': '43181107364617000135550000000048051004621865', 'xml':[...]