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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_open_file(self, file_des):
 """Return an open file. Args: file_des: File descriptor of the open file. Raises: OSError: an invalid file descriptor. TypeError: filedes is not an integer. Returns: Open file object. """

        if not is_int_type(file_des):
            raise TypeError('an integer is required')
        if (file_des >= len(self.open_files) or
                self.open_files[file_des] is None):
            self.raise_os_error(errno.EBADF, str(file_des))
        return self.open_files[file_des][0]