How to use the sourcegraph.app function in sourcegraph

// Implementations panel.
    const IMPL_ID = 'go.impl' // implementations panel and provider ID
    ctx.subscriptions.add(
        sourcegraph.languages.registerLocationProvider(IMPL_ID, [{ pattern: '*.go' }], {
            provideLocations: async (doc: sourcegraph.TextDocument, pos: sourcegraph.Position) => {
                const response = await sendRequest({
                    rootURI: rootURIFromDoc(doc),
                    requestType: lspProtocol.ImplementationRequest.type,
                    request: positionParams(doc, pos),
                    useCache: true,
                })
                return convert.references({ currentDocURI: doc.uri, references: response })
            },
        })
    )
    const panelView = sourcegraph.app.createPanelView(IMPL_ID)
    panelView.title = 'Go ifaces/impls'
    panelView.component = { locationProvider: IMPL_ID }
    panelView.priority = 160
    ctx.subscriptions.add(panelView)
}

import * as sourcegraph from 'sourcegraph'
import { codecovToDecorations } from './decoration'
import {
    getCommitCoverageRatio,
    getFileCoverageRatios,
    getFileLineCoverage,
} from './model'
import { resolveEndpoint, resolveSettings, Settings } from './settings'
import {
    codecovParamsForRepositoryCommit,
    resolveDocumentURI,
    resolveRootURI,
} from './uri'

const decorationType =
    sourcegraph.app.createDecorationType &&
    sourcegraph.app.createDecorationType()

/** Entrypoint for the Codecov Sourcegraph extension. */
export function activate(): void {
    function activeEditors(): sourcegraph.CodeEditor[] {
        return sourcegraph.app.activeWindow
            ? sourcegraph.app.activeWindow.visibleViewComponents
            : []
    }

    // When the configuration or current file changes, publish new decorations.
    //
    // TODO: Unpublish decorations on previously (but not currently) open files when settings changes, to avoid a
    // brief flicker of the old state when the file is reopened.
    async function decorate(editors = activeEditors()): Promise {
        const settings = resolveSettings(

function activeEditors(): sourcegraph.CodeEditor[] {
        return sourcegraph.app.activeWindow
            ? sourcegraph.app.activeWindow.visibleViewComponents
            : []
    }

}
                    const implementationResult = (await sendTracedRequest(
                        connection,
                        ImplementationRequest.type,
                        implementationParams,
                        { span, tracer, token }
                    )) as Location[] | Location | null
                    rewriteUris(implementationResult, toSourcegraphTextDocumentUri)
                    return convertLocations(implementationResult)
                })
            providers.add(
                sourcegraph.languages.registerLocationProvider(IMPL_ID, documentSelector, {
                    provideLocations: provideImpls,
                })
            )
            const panelView = sourcegraph.app.createPanelView(IMPL_ID)
            panelView.title = 'Implementations'
            panelView.component = { locationProvider: IMPL_ID }
            panelView.priority = 160
            providers.add(panelView)
        }
    }
}

? new LightstepTracer({ access_token: config.value['lightstep.token'], component_name: 'ext-lang-typescript' })
        : new Tracer()

    const accessToken = await getOrCreateAccessToken()
    /** The Sourcegraph endpoint contactable by the server */
    const serverSgEndpoint: SourcegraphEndpoint = {
        url: new URL(config.value['typescript.sourcegraphUrl'] || sourcegraph.internal.sourcegraphURL.toString()),
        accessToken,
    }
    /** The Sourcegraph endpoint contactable by the extension  */
    const clientSgEndpoint: SourcegraphEndpoint = {
        url: new URL(sourcegraph.internal.sourcegraphURL.toString()),
        accessToken,
    }

    const diagnosticsDecorationType = sourcegraph.app.createDecorationType()
    const codeActionsDecorationType = sourcegraph.app.createDecorationType()

    sourcegraph.commands.registerCommand('typescript.toggle', async () => {
        const config = sourcegraph.configuration.get()
        await config.update('typescript.enable', config.value['typescript.enable'] === false)
    })

    const enabled = new BehaviorSubject(config.value['typescript.enable'] !== false)
    ctx.subscriptions.add(
        from(config)
            .pipe(
                rxop.map(config => config['typescript.enable'] !== false),
                rxop.distinctUntilChanged()
            )
            .subscribe(enabled)
    )