docs: add docstring to PbcClient for better self-documentation

pbc_client/__init__.py

@@ -68,6 +68,40 @@ class Balances:
 
 @dataclasses.dataclass(frozen=True)
 class PbcClient:
+    """
+    PbcClient provides an interface to interact with the Partisia Blockchain.
+
+    It supports various operations such as sending transactions (both raw and signed),
+    retrieving account balances, fetching blockchain metadata (e.g., chain ID, nonces),
+    and obtaining contract state details.
+
+    Attributes:
+        session (requests.Session): The HTTP session used for all network communications.
+
+    Methods:
+        send_transaction(contract_address: str, rpc: bytes, gas_cost: int)
+            Sends a transaction request to the blockchain.
+
+        send_signed_transaction(signed_transaction: SignedTransaction)
+            Dispatches a pre-signed transaction to the blockchain.
+
+        get_account_balances(address: str) -> Balances
+            Retrieves the balance information for the given account.
+
+        get_chain_id() -> str
+            Returns the blockchain's chain identifier.
+
+        get_sender_authentication_nonce() -> int
+            Obtains the nonce for sender authentication.
+
+        get_nonce_for_account(address: str) -> int
+            Retrieves the nonce for the specified account.
+
+        get_contract_state(address: str) -> tuple[dict, datetime.datetime]
+            Fetches the state and timestamp of a given contract.
+
+        ... (other public methods are similarly available)
+    """
     session: requests.Session
     sender_authentication: SenderAuthentication | None = None
     hostname: str = HOSTNAME_MAINNET