str: TissueMAPS system group (defaults to
        :attr:`tm_user <tmdeploy.config.AnsibleHostVariableSection.tm_user>`)

def tm_group(self):
        '''str: TissueMAPS system group (defaults to
        :attr:`tm_user <tmdeploy.config.AnsibleHostVariableSection.tm_user>`)
        '''
        if self._tm_group is None:
            self._tm_group = self.tm_user
        return self._tm_group