Callables that provide message filters for the MetlogClient. Each provider accepts needed filter configuration values, and returns a filter function usable by a MetlogClient instance.
Each filter accepts a single msg dictionary argument and returns a boolean value: True if a message should be delivered, False if a message should not be delivered. Note that the msg dictionary may be mutated by the filter.
Filter if message severity is greater than specified severity.
Filter if message type is in the types value.
Filter if message type has specified maximum severity value and message severity is higher than this maximum. Each keyword argument key should be a message type name, and each keyword argument value should be the maximum allowed severity for that message type.