Create a Function to check if the entire chain is valid.

Make your changes to the function:

is_chain_valid(self, chain)

in "Defining Blockchain and C-coin.py"

Open "Defining Blockchain and C-coin.py" and read the surrounding blockchain and chain-representation code before examining is_chain_valid(self, chain). Trace how the chain is created and used to determine the validation expectations; done means the function checks the entire chain consistently with those existing behaviors.

Written by the indexing model from the issue text.