Aggregate deep nested mongo

mongo_statistic_agg.js

db.getCollection('article').aggregate([
    {$match: {$or: [
        {"view.sections.parts.embed.provider_name": {$in: ['Commerce Product', 'Image With Hotspots', 'Commerce Product Group']}},
        {"view.sections.steps.parts.embed.provider_name": {$in: ['Commerce Product', 'Image With Hotspots', 'Commerce Product Group']}}
    ]}},
    {$project: {_id: 1}
])

db.getCollection('article').aggregate([
    {$match: {$or: [
        {"view.sections.parts.embed.provider_name": {$in: ['Commerce Product', 'Image With Hotspots', 'Commerce Product Group']}},
        {"view.sections.steps.parts.embed.provider_name": {$in: ['Commerce Product', 'Image With Hotspots', 'Commerce Product Group']}}
    ]}},
    {$project: {
        "provider_names": {
            $reduce: {
                input: {$concatArrays: [
                    {$ifNull: ["$view.sections.parts.embed.provider_name", []]},
                    {$ifNull: ["$view.sections.steps.parts.embed.provider_name", []]}
                ]},
                initialValue: [],
                in: { $concatArrays : ["$$value", "$$this"] }
            }
        }
    }}
])