<human>:  check that can open file.
<bot>: Here is a Python function to check that can open a file

import os

def check_open(filename):
  """
  Check if the file is open
  Returns True if file is open else False
  """
  if os.path.isfile(filename):
    return True
  else:
    return False

# Enter the filename
filename = 'test.txt'

# Calling the function
print((check_open(filename)))

#Example Output
# True

#Remember to inspect code for bugs.