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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 write(self, file_or_filename, prog=None, format='xdot'):
 """ Writes the case data in Graphviz DOT language. The format 'raw' is used to dump the Dot representation of the Case object, without further processing. The output can be processed by any of graphviz tools, defined in 'prog'. """

        if prog is None:
            file = super(DotWriter, self).write(file_or_filename)
        else:
            buf = StringIO.StringIO()
            super(DotWriter, self).write(buf)
            buf.seek(0)
            data = self.create(buf.getvalue(), prog, format)

            if isinstance(file_or_filename, basestring):
                file = None
                try:
                    file = open(file_or_filename, "wb")
                except:
                    logger.error("Error opening %s." % file_or_filename)
                finally:
                    if file is not None:
                        file.write(data)
                        file.close()
            else:
                file = file_or_filename
                file.write(data)

        return file