Add StatsBase.predict to the interface (#81)

* Add StatsBase as a dependency

* Implement StatsBase.predict

* use `fix` and fix some errors

* Format

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Bump StatsBase compat

* slim down implementations

---------

Co-authored-by: Hong Ge <[email protected]>
Co-authored-by: Xianda Sun <[email protected]>
Co-authored-by: Xianda Sun <[email protected]>
Co-authored-by: Penelope Yong <[email protected]>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Project.toml

@@ -11,11 +11,13 @@ Accessors = "7d9f7c33-5ae7-4f3b-8dc6-eff91059b697"
 DensityInterface = "b429d917-457f-4dbc-8f4c-0cc954292b1d"
 JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 
 [compat]
 AbstractMCMC = "2, 3, 4, 5"
 Accessors = "0.1"
 DensityInterface = "0.4"
 JSON = "0.19 - 0.21"
 Random = "1.6"
+StatsBase = "0.32, 0.33, 0.34"
 julia = "~1.6.6, 1.7.3"

src/abstractprobprog.jl

@@ -1,6 +1,7 @@
 using AbstractMCMC
 using DensityInterface
 using Random
+using StatsBase
 
 """
     AbstractProbabilisticProgram
@@ -116,3 +117,16 @@ end
 function Base.rand(model::AbstractProbabilisticProgram)
     return rand(Random.default_rng(), NamedTuple, model)
 end
+
+"""
+    predict(
+        [rng::AbstractRNG=Random.default_rng(),]
+        model::AbstractProbabilisticProgram,
+        params,
+    )
+
+Draw a sample from the predictive distribution specified by `model` with its parameters fixed to `params`.
+"""
+function StatsBase.predict(model::AbstractProbabilisticProgram, params)
+    return predict(Random.default_rng(), NamedTuple, model, params)
+end