code: def generate_const(self):
          
          const = self._definition['const']
          if isinstance(const, str):
              const = '"{}"'.format(const)
          with self.l('if {variable} != {}:', const):
              self.l('raise JsonSchemaException("{name} must be same as const definition")')
docs: Means that value is valid when is equeal to const definition.
  
          .. code-block:: python
  
              {
                  'const': 42,
              }
  
          Only valid value is 42 in this example.