1:-einvoice.py file is main script. syntax for execute the script is "python3 einvoice.py". Before execute the script you need to follw below point.

i) You need to put GSTIN info(gstin,einv_username,einv_password) in GstinInfo  in constant.py file.
ii) You need to put credential details(username,password,client_id,client_secret) provide by masters india in accessTokenInfo  in constant.py file.
iii) You need to uncomment the function which you want to execute.
iv) host variable in constant.py for sandbox will be "https://api.mastersindia.co". For production, it will be "https://proapi.mastersindia.co".
v) NIC encryption public key(Einv_publickey.pem) file is different for both environment sandbox and production.
vi) Generate IRN and cancel IRN JSON is present in constant.py. you need to change DocDtls No in JSON to generate IRN.
vii) At the time of generate, cancel and get IRN you need to pass auth_token, sek which is received in einvoice auth token API and flat_app_key which is used in einvocie auth token API.