# Functions
NewImpressionManager creates new ImpManager.
NewImpressionObserver constructs a new ImpressionObserver.
NewImpressionsCounter creates new ImpressionsCounter.
# Structs
ImpressionHasherImpl implements the hasher interface, mapping certain fields to an int64.
ImpressionManagerImpl implements.
ImpressionObserverImpl is an implementation of the ImpressionObserver interface.
ImpressionObserverNoOp is an implementation of the ImpressionObserver interface.
ImpressionsCounter struct for storing generated impressions counts.
Key struct for mapping each key to an amount.
# Interfaces
ImpressionHasher interface.
ImpressionManager interface.
ImpressionObserver is used to check wether an impression has been previously seen.