Clarify that using block_identifier with .call() comes with its caveats (#2048)

* Clarify that using `block_identifier` with .call() comes with its caveats
To manage the expectations of the client library users.

Author: miohtama

docs/contracts.rst

@@ -827,6 +827,11 @@ Methods
         # You can check the state after your pending transactions (if supported by your node):
         >>> token_contract.functions.myBalance().call(block_identifier='pending')
 
+    Passing the ``block_identifier`` parameter for past block numbers requires that your Ethereum API node
+    is running in the more expensive archive node mode. Normally synced Ethereum nodes will fail with
+    a "missing trie node" error, because Ethereum node may have purged the past state from its database.
+    `More information about archival nodes here <https://ethereum.stackexchange.com/a/84200/620>`_.
+
 .. py:method:: ContractFunction.estimateGas(transaction, block_identifier=None)
 
     Call a contract function, executing the transaction locally using the

newsfragments/2048.doc.rst

@@ -0,0 +1,2 @@
+Clarify that a missing trie node error could occur when using ``block_identifier`` with ``.call()``
+on a node that isn't running in archive mode