code: def get_mapping_variable(variable_name, variables_mapping):
      
      try:
          return variables_mapping[variable_name]
      except KeyError:
          raise exceptions.VariableNotFound("{} is not found.".format(variable_name))
docs: get variable from variables_mapping.
  
      Args:
          variable_name (str): variable name
          variables_mapping (dict): variables mapping
  
      Returns:
          mapping variable value.
  
      Raises:
          exceptions.VariableNotFound: variable is not found.