How to submit form with the help of Python mechanize to get the output.?

I don't know much about the mechanize; I have several text files that I want to upload to a web tool to get the results. I tried submitting with a fasta/text file and the corresponding input parameters. I am using the following python code:

controls of this form are

import requests
import os
import mechanized
import csv
 
loc="C:/Users/Binni/Documents/Provean/"
files=os.listdir(loc)

br = mechanize.Browser()
br.set_handle_robots(False) 
br.set_handle_refresh(False)
url = "https://snps.biofold.org/meta-snp/"
br.open(url)

For file in files:
            #print(file)
            if file == "SP11_00001.fasta":
             ip=os.path.join(loc,file)
             With open(ip) as f:
                data = f.read()
                #print(data)

br.select_form(nr=0)
print(br.form)
#br.form.add_file(open(ip), 'text/plain', ip, name = 'seqfile')
br['proteina'] = data 
br['posizione'] = "L229F"
print(br.form)
response = br.submit()

I got the results with sample input files directly uploaded on the web tool. I am getting the web tools error "Incorrect Aminoacid Position" with the above python scripts. Please help me to solve this issue.