Return the number of simple/default contracts.

    Simple contracts are the ones which raise a RuntimeError with message
    'Argument `*[argument_name]*` is not valid'

def _get_num_contracts(contracts_list, param_name):
    """
    Return the number of simple/default contracts.

    Simple contracts are the ones which raise a RuntimeError with message
    'Argument `*[argument_name]*` is not valid'
    """
    msg = "Argument `*[argument_name]*` is not valid"
    return sum(
        [
            1 if item["msg"] == msg.replace("*[argument_name]*", param_name) else 0
            for item in contracts_list
        ]
    )