Flutter Podfile and Firebase

Where in the Podfile should pod 'Firebase/Core' be placed? It's obvious when the Podfile looks like this:

# Uncomment this line to define a global platform for your project
# platform :ios, '9.0'
target 'Runner' do
  # Uncomment this line if you're using Swift or would like to use dynamic frameworks
  # use_frameworks!
  # Pods for Runner
  pod 'MaterialControls', '~> 1.2.2'
end

But the default Podfile for my project looks like this:

# Uncomment this line to define a global platform for your project
# platform :ios, '9.0'

# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'

def parse_KV_file(file, separator='=')
  file_abs_path = File.expand_path(file)
  if !File.exists? file_abs_path
    return [];
  end
  pods_ary = []
  skip_line_start_symbols = ["#", "/"]
  File.foreach(file_abs_path) { |line|
      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
      plugin = line.split(pattern=separator)
      if plugin.length == 2
        podname = plugin[0].strip()
        path = plugin[1].strip()
        podpath = File.expand_path("#{path}", file_abs_path)
        pods_ary.push({:name => podname, :path => podpath});
      else
        puts "Invalid plugin specification: #{line}"
      end
  }
  return pods_ary
end

target 'Runner' do
  use_frameworks!

  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
  # referring to absolute paths on developers' machines.
  system('rm -rf .symlinks')
  system('mkdir -p .symlinks/plugins')

  # Flutter Pods
  generated_xcode_build_settings = parse_KV_file('./Flutter/Generated.xcconfig')
  if generated_xcode_build_settings.empty?
    puts "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
  end
  generated_xcode_build_settings.map { |p|
    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
      symlink = File.join('.symlinks', 'flutter')
      File.symlink(File.dirname(p[:path]), symlink)
      pod 'Flutter', :path => File.join(symlink, File.basename(p[:path]))
    end
  }

  # Plugin Pods
  plugin_pods = parse_KV_file('../.flutter-plugins')
  plugin_pods.map { |p|
    symlink = File.join('.symlinks', 'plugins', p[:name])
    File.symlink(p[:path], symlink)
    pod p[:name], :path => File.join(symlink, 'ios')
  }
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings['ENABLE_BITCODE'] = 'NO'
    end
  end
end

And, admittedly, I can't quite decipher it enough to determine where to place it. Does it go inside the target 'Runner' do block right after use_frameworks!? Or perhaps at the top of the file right after ENV['COCOAPODS_DISABLE_STATS'] = 'true'? Any guidance would be greatly appreciated. Also, if you can shed any light on the code itself, that would be a welcome bonus.