ImportError: Field Order, while importing items

while importing items from doctype Field Order to doctype Order Book’s child table i’m getting this error i.e ImportError: Field Order.
Screenshot_2020-01-30%20New%20Order%20Book%201

order_book.js code:

frappe.ui.form.on(‘Order Book’, {

refresh: function(frm, dt, dn) {
	frm.add_custom_button(__('Customer Credit Balance'), function() {
        frappe.set_route('query-report', 'Customer Credit Balance', {Customer:frm.doc.name});
    })

    console.log("=========doc",frm.doc,"====date",frm.doc.date);

    if (frm.doc.docstatus==0) {
        frm.add_custom_button(__('Field Order'),
            function() {
                erpnext.utils.map_current_doc({
                    method: "dairy.field_order.doctype.field_order.field_order.make_order_book",
                    source_doctype: "Field Order",
                    target: frm,
                    setters: [ 
                        {
                            label: "Customer",
                            fieldname: "customer",
                            fieldtype: "Link",
                            options: "Customer",
                            default: frm.doc.customer || undefined
                        }
                    ],
                    get_query_filters: {
                        company: frm.doc.company,
                        docstatus: 1,
                        disable: 0
                    }
                })
            }, __("Get items from"));
    }
    order_type(doc);
},

field_order.py code:

@frappe.whitelist()

def make_order_book(source_name, target_doc=None):
field_order = frappe.db.get_value(“Field Order”, source_name, “transaction_date”, as_dict = 1)

def set_missing_values(source, target):
	order_book = frappe.get_doc(target)

	target.append('order_book_line', {
		'sales_team': source.user,
		'customer': source.customer,
		'econdary_customer': source.customer,
		'product': source.item,
		'qty':source.qty,
		'uom':source.uom
	})


def update_item(obj, target, source_parent):
	target.stock_qty = flt(obj.qty) * flt(obj.conversion_factor)

doclist = get_mapped_doc("Field Order", source_name, {
		"Field Order": {
			"doctype": "Order Book",
			"validation": {
				"docstatus": ["=", 1]
			}
		},

		"Field Order": {
		    "doctype": "Order Book Line",
		    "field_map": {
				"parent": "prevdoc_docname"	
		    },
		    "postprocess": update_item
		}

	}, target_doc, set_missing_values)
	 
return doclist