FilterFromOperator creates a new filter with the given operator.

MustParse is like Parse but panics if parse fails.

Parse returns a filter based on key, value, and operator Argument patterns: `"key"` - Will match if the key is found `"keyOPvalue"` - Where OP is one or more none-word characters, will check the value of key against the provided value using the operator `"key", "op", "value"` - Will check the value at key against the value using the operator.