Get retention policy assignment

{
  "type": "object",
  "description": "A retention assignment represents a rule specifying\nthe files a retention policy retains.\nAssignments can retain files based on their folder or metadata,\nor hold all files in the enterprise.",
  "properties": {
    "assigned_at": {
      "type": "string",
      "format": "date-time",
      "description": "When the retention policy assignment object was\ncreated."
    },
    "assigned_by": {
      "type": "object"
    },
    "assigned_to": {
      "type": "object",
      "description": "The `type` and `id` of the content that is under\nretention. The `type` can either be `folder`\n`enterprise`, or `metadata_template`.",
      "properties": {
        "id": {
          "type": "string",
          "description": "The ID of the folder, enterprise, or metadata template\nthe policy is assigned to."
        },
        "type": {
          "type": "string",
          "description": "The type of resource the policy is assigned to.",
          "enum": [
            "folder",
            "enterprise",
            "metadata_template"
          ]
        }
      }
    },
    "filter_fields": {
      "type": "array",
      "description": "An array of field objects. Values are only returned if the `assigned_to`\ntype is `metadata_template`. Otherwise, the array is blank.",
      "items": {
        "type": "object",
        "properties": {
          "field": {
            "type": "string",
            "description": "The metadata attribute key id."
          },
          "value": {
            "type": "string",
            "description": "The metadata attribute field id. For value, only\nenum and multiselect types are supported."
          }
        }
      }
    },
    "id": {
      "type": "string",
      "description": "The unique identifier for a retention policy assignment."
    },
    "retention_policy": {
      "type": "object"
    },
    "start_date_field": {
      "type": "string",
      "description": "The date the retention policy assignment begins."
    },
    "type": {
      "type": "string",
      "description": "`retention_policy_assignment`",
      "enum": [
        "retention_policy_assignment"
      ]
    }
  }
}