Using the show-prelude option in the verify-policy command still require the path to the policy file

[tromai]

Description
In the verify-policy action, there is the --show-prelude flag for dumping out the policy preclude.
In this method, it indicates that showing the preclude does not require any user policy file - https://github.com/oracle-samples/macaron/blob/907eedf543131a2dd8d406bfa3ad54b3df8fae9a/src/macaron/policy_engine/policy_engine.py#L159 .
However, when we try to use the --show-prelude flag, this error happens:

usage: macaron verify-policy [-h] -d DATABASE -f FILE [-s]
macaron verify-policy: error: the following arguments are required: -f/--file