added support for new testnets in blockfrost (#80)

* added support for new testnets in blockfrost

* reformat files

* removed unused import

* Revert "added support for new testnets in blockfrost"

This reverts commit 729ebc7.

* added option to use custom blockfrost base url

pycardano/backend/blockfrost.py

@@ -43,11 +43,15 @@ class BlockFrostChainContext(ChainContext):
         network (Network): Network to use.
     """
 
-    def __init__(self, project_id: str, network: Network = Network.TESTNET):
+    def __init__(
+        self, project_id: str, network: Network = Network.TESTNET, base_url: str = None
+    ):
         self._network = network
         self._project_id = project_id
         self._base_url = (
-            ApiUrls.testnet.value
+            base_url
+            if base_url
+            else ApiUrls.testnet.value
             if self.network == Network.TESTNET
             else ApiUrls.mainnet.value
         )
@@ -176,7 +180,10 @@ def utxos(self, address: str) -> List[UTxO]:
 
             script = None
 
-            if hasattr(result, "reference_script_hash") and result.reference_script_hash:
+            if (
+                hasattr(result, "reference_script_hash")
+                and result.reference_script_hash
+            ):
                 script = self._get_script(result.reference_script_hash)
 
             tx_out = TransactionOutput(