how to accept file or path as arguments to method in python

I am trying to write a method that will accept either an opened file

myFile = open("myFile.txt")
 obj.writeTo(myFile)
 myFile.close()
 

or a string with a path

obj.writeTo("myFile.txt")
 

The method is implemented as follows:

def writeTo(self, hessianFile):
     if isinstance(hessianFile,file):
         print("File type")
     elif isinstance(hessianFile,str):
         print("String type")
     else:
         pass
 

But this raises an error

NameError: global name 'file' is not defined
 

why is file type not defined? Shouldn't file be defined all the time? How should the implementation be corrected to properly handel both path an file as valid argument types

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