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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 _generate_hash(self):
 """ Generates a hash based on the specific fields for the method. """

        
        self.hash = None
        str_hash = ''
        
        for key, val in self._get_params().iteritems():
            str_hash += smart_str(val)
        
        # Append the encryption string
        str_hash += self._service.encryption_key
        
        # Set md5 hash on the object
        self.hash = hashlib.md5(str_hash).hexdigest()