The documentation for asyncio.create_subprocess_exec says this is the definition . . .

asyncio.create_subprocess_exec(*args, stdin=None, stdout=None, stderr=None, loop=None, limit=None, **kwds)

The actual definition is this . . .

def create_subprocess_exec(program, *args, stdin=None, stdout=None,            
                           stderr=None, loop=None,                             
                           limit=streams._DEFAULT_LIMIT, **kwds)

Notice the first argument (program) at the start of the actual definition.