implement a map for outgoing streams

vendor/github.com/cheekybits/genny/generic/doc.go

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+// Package generic contains the generic marker types.
+package generic

vendor/github.com/cheekybits/genny/generic/generic.go

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+package generic
+
+// Type is the placeholder type that indicates a generic value.
+// When genny is executed, variables of this type will be replaced with
+// references to the specific types.
+//      var GenericType generic.Type
+type Type interface{}
+
+// Number is the placehoder type that indiccates a generic numerical value.
+// When genny is executed, variables of this type will be replaced with
+// references to the specific types.
+//      var GenericType generic.Number
+type Number float64