'Check the validity of a Block\'s signature.
Returns:
bool: Stating the validity of the Block\'s signature.'

def is_signature_valid(self):

    block = self.to_dict()['block']
    block_serialized = serialize(block).encode()
    public_key = PublicKey(block['node_pubkey'])
    try:
        return public_key.verify(block_serialized, self.signature)
    except (ValueError, AttributeError):
        return False
