Add file to column using add_file_to_column

I haven’t found more or less useful example how to use add_file_to_column in GraphQL, so I have tried the following code.


mutation add_file{
		column_id: "dup__of_prd", 
		file: {url:""}


I got 500 Internal server error and it is more understandable issue during my exercises.

Can you help me to understand the mistake or share good examples how to call add_file_to_column in the tight way?
The most critical for me is understanding the using of File! parameter/variable.