Rewrite all rest examples according to v3.0.0b3's changes.

examples/rest/merchant/submit_invoice.py

@@ -2,12 +2,10 @@
 
 import os
 
-from bfxapi import Client, REST_HOST
-
+from bfxapi import Client
 from bfxapi.types import InvoiceSubmission
 
 bfx = Client(
-    rest_host=REST_HOST,
     api_key=os.getenv("BFX_API_KEY"),
     api_secret=os.getenv("BFX_API_SECRET")
 )
@@ -20,7 +18,7 @@ customer_info = {
     "residStreet": "5-6 Leicester Square",
     "residBuildingNo": "23 A",
     "fullName": "John Doe",
-    "email": "john@example.com"
+    "email": "john@example.com",
 }
 
 invoice: InvoiceSubmission = bfx.rest.merchant.submit_invoice(
@@ -29,17 +27,19 @@ invoice: InvoiceSubmission = bfx.rest.merchant.submit_invoice(
     order_id="test",
     customer_info=customer_info,
     pay_currencies=["ETH"],
-    duration=86400 * 10
+    duration=86400,
 )
 
 print("Invoice submission:", invoice)
 
-print(bfx.rest.merchant.complete_invoice(
-    id=invoice.id,
-    pay_currency="ETH",
-    deposit_id=1
-))
+print(
+    bfx.rest.merchant.complete_invoice(id=invoice.id, pay_currency="ETH", deposit_id=1)
+)
 
 print(bfx.rest.merchant.get_invoices(limit=25))
 
-print(bfx.rest.merchant.get_invoices_paginated(page=1, page_size=60, sort="asc", sort_field="t"))
+print(
+    bfx.rest.merchant.get_invoices_paginated(
+        page=1, page_size=60, sort="asc", sort_field="t"
+    )
+)