code: def get_product_inventory(product_id, warehouse_ids):
      
      Product = client.model('product.product')
  
      return Product.get_product_inventory(
          [product_id], warehouse_ids
      )[product_id]
docs: Return the product inventory in each location. The returned response
      will look like::
  
          {
              12: {       // Product ID
                  4: {    // Location ID
                      'quantity_on_hand': 12.0,
                      'quantity_available': 8.0
                  },
                  5: {    // Location ID
                      'quantity_on_hand': 8.0,
                      'quantity_available': 8.0
                  },
              },
              126: {      // Product ID
                  4: {    // Location ID
                      'quantity_on_hand': 16.0,
                      'quantity_available': 15.0
                  },
                  5: {    // Location ID
                      'quantity_on_hand': 9.0,
                      'quantity_available': 8.0
                  },
              }
          }
  
      Read more:
      http://docs.fulfiliorestapi.apiary.io/#reference/product/product-inventory