Why do I get the error, module object is not callable when calling csv writer using tabulate?

import tabulate
import sys
import csv

def main():
    if len(sys.argv) == 1:
        sys.exit('Too few command-line arguments')
    elif len(sys.argv) > 2:
        sys.exit('Too many command-line arguments')
    elif not sys.argv[1].endswith('.csv'):
        sys.exit('Not a CSV file')
    elif len(sys.argv) == 2:
        try:
            with open(sys.argv[1], 'w') as csvfile:
                writer = csv.writer(csvfile)
                writer.writerow(tabulate(writerwriter, header="firstrow", tablefmt="grid"))
        except FileNotFoundError:
            sys.exit('File does not exist')


if __name__ == '__main__':
    main()

I want to print a tabulated version of an inputted csv file in the command line. It should open the file in write mode, and then re-write that file in a tabulated graph format with the header as the first line. However, when I run the graph, I get:

Traceback (most recent call last):
  File "/workspaces/112136537/pizza/pizza.py", line 22, in <module>
    main()
  File "/workspaces/112136537/pizza/pizza.py", line 16, in main
    spamwriter.writerow(tabulate(spamwriter, header="firstrow", tablefmt="grid"))
TypeError: 'module' object is not callable

Why can't the module be called?