code: public void createPackageContents()
    {
      if (isCreated) return;
      isCreated = true;
  
      // Create classes and their features
      ifConditionEClass = createEClass(IF_CONDITION);
      createEAttribute(ifConditionEClass, IF_CONDITION__ELSEIF);
      createEReference(ifConditionEClass, IF_CONDITION__CONDITION);
  
      expressionEClass = createEClass(EXPRESSION);
  
      numberLiteralEClass = createEClass(NUMBER_LITERAL);
      createEAttribute(numberLiteralEClass, NUMBER_LITERAL__VALUE);
  
      booleanLiteralEClass = createEClass(BOOLEAN_LITERAL);
      createEAttribute(booleanLiteralEClass, BOOLEAN_LITERAL__VALUE);
  
      methodCallEClass = createEClass(METHOD_CALL);
      createEAttribute(methodCallEClass, METHOD_CALL__VALUE);
  
      orExpressionEClass = createEClass(OR_EXPRESSION);
      createEReference(orExpressionEClass, OR_EXPRESSION__LEFT);
      createEReference(orExpressionEClass, OR_EXPRESSION__RIGHT);
  
      andExpressionEClass = createEClass(AND_EXPRESSION);
      createEReference(andExpressionEClass, AND_EXPRESSION__LEFT);
      createEReference(andExpressionEClass, AND_EXPRESSION__RIGHT);
  
      comparisonEClass = createEClass(COMPARISON);
      createEReference(comparisonEClass, COMPARISON__LEFT);
      createEAttribute(comparisonEClass, COMPARISON__OPERATOR);
      createEReference(comparisonEClass, COMPARISON__RIGHT);
  
      notExpressionEClass = createEClass(NOT_EXPRESSION);
      createEReference(notExpressionEClass, NOT_EXPRESSION__EXPRESSION);
    }
docs: Creates the meta-model objects for the package.  This method is
  guarded to have no affect on any invocation but its first.
  <!-- begin-user-doc -->
  <!-- end-user-doc -->
  @generated