validate
Adds a validator that checks each element in the set against the given predicate.
Parameters
message
Template message for validation errors. Supports:
@name: property name
@value: the invalid element value (properly formatted)
@switches: option switches (e.g. "--port|-p")
predicate
Function that returns true if the element is valid
Adds multiple element validators at once.
Parameters
validations
Pairs of (message template, predicate) for element validation