Hello Gowtham A,

I hope you're doing well.

The error occurs because self.writing_file_transfer is a boolean (True or False), and you're trying to concatenate it with a string   (str(self.id) + '.csv'). Since Python does not allow direct concatenation of a boolean and a string, it raises a TypeError.

Convert self.writing_file_transfer to a string before concatenation:

{'name': str(self.writing_file_transfer) + str(self.id) + '.csv', 'type': 'binary', 'public': True,

'datas': base64.encodebytes(fp.getvalue()), }

I hope this resolves your issue.

Thanks & Regards,

Email:  odoo@aktivsoftware.com           

Skype: kalpeshmaheshwari

if you check type of 

self.writing_file_transfer	​

its may Boolean and you are trying to add Boolean and string 
try this :

str(self.writing_file_transfer)