code: def to_json(self, variables=None):
          
  
          variables_to_resolve = []
          if variables:
              for key, value in variables.items():
                  variables_to_resolve.append(Variable(key, value))
          for k in self.get_parameter_definitions():
              if not variables or k not in variables:
                  # The provided value for a CFN parameter has no effect in this
                  # context (generating the CFN template), so any string can be
                  # provided for its value - just needs to be something
                  variables_to_resolve.append(Variable(k, 'unused_value'))
          self.resolve_variables(variables_to_resolve)
  
          return self.render_template()[1]
docs: Render the blueprint and return the template in json form.
  
          Args:
              variables (dict):
                  Optional dictionary providing/overriding variable values.
  
          Returns:
              str: the rendered CFN JSON template