Compile Error: 'Segment' is a namespace but is used like a type

[ysalpha2021]

I get a compile error when I try to use it with a package called Segment (https://segment.com/docs/)
Library\PackageCache\com.unity.uiextensions\Editor\UIExtensionsMenuOptions.cs(1831,36): error CS0118: 'Segment' is a namespace but is used like a type

This is caused by the following namespace in Segment Package.
using Segment.Serialization;
using Segment.Analytics.Analytics;

uiextensions are obtained via Package Manager
"com.unity.uiextensions": "https://bitbucket.org/UnityUIExtensions/unity-ui-extensions.git"

What measures could be taken to resolve the compilation error?