fix: remove redundant cast and update public API

Author: MaggieKimani1

src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs

@@ -295,13 +295,13 @@ public bool Contains(string location)
             var uri = ToLocationUrl(location);
             if (uri is not null)
             {
-                if (_IOpenApiReferenceableRegistry.TryGetValue(uri, out var referenceableValue))
+                if (_IOpenApiReferenceableRegistry.TryGetValue(uri, out var referenceableValue) && referenceableValue is T referenceable)
                 {
-                    return (T)referenceableValue;
+                    return referenceable;
                 }
-                else if (_artifactsRegistry.TryGetValue(uri, out var artifact))
+                else if (_artifactsRegistry.TryGetValue(uri, out var artifact) && artifact is T artifactValue)
                 {
-                    return (T)(object)artifact;
+                    return artifactValue;
                 }
             }            
 

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -1915,7 +1915,7 @@ namespace Microsoft.OpenApi.Writers
         void WriteValue(decimal value);
         void WriteValue(int value);
         void WriteValue(object value);
-        void WriteValue(string? value);
+        void WriteValue(string value);
     }
     public class OpenApiJsonWriter : Microsoft.OpenApi.Writers.OpenApiWriterBase
     {
@@ -1927,11 +1927,11 @@ namespace Microsoft.OpenApi.Writers
         public override void WriteEndObject() { }
         public override void WriteIndentation() { }
         public override void WriteNull() { }
-        public override void WritePropertyName(string? name) { }
+        public override void WritePropertyName(string name) { }
         public override void WriteRaw(string value) { }
         public override void WriteStartArray() { }
         public override void WriteStartObject() { }
-        public override void WriteValue(string? value) { }
+        public override void WriteValue(string value) { }
         protected override void WriteValueSeparator() { }
     }
     public class OpenApiJsonWriterSettings : Microsoft.OpenApi.Writers.OpenApiWriterSettings
@@ -1962,13 +1962,13 @@ namespace Microsoft.OpenApi.Writers
         protected bool IsObjectScope() { }
         protected bool IsTopLevelScope() { }
         protected Microsoft.OpenApi.Writers.Scope StartScope(Microsoft.OpenApi.Writers.ScopeType type) { }
-        protected void VerifyCanWritePropertyName(string? name) { }
+        protected void VerifyCanWritePropertyName(string name) { }
         public abstract void WriteEndArray();
         public abstract void WriteEndObject();
         public virtual void WriteEnumerable<T>(System.Collections.Generic.IEnumerable<T> collection) { }
         public virtual void WriteIndentation() { }
         public abstract void WriteNull();
-        public abstract void WritePropertyName(string? name);
+        public abstract void WritePropertyName(string name);
         public abstract void WriteRaw(string value);
         public abstract void WriteStartArray();
         public abstract void WriteStartObject();
@@ -1981,7 +1981,7 @@ namespace Microsoft.OpenApi.Writers
         public virtual void WriteValue(int value) { }
         public virtual void WriteValue(long value) { }
         public virtual void WriteValue(object? value) { }
-        public abstract void WriteValue(string? value);
+        public abstract void WriteValue(string value);
         protected abstract void WriteValueSeparator();
         public static void WriteV2Examples(Microsoft.OpenApi.Writers.IOpenApiWriter writer, Microsoft.OpenApi.Models.OpenApiExample example, Microsoft.OpenApi.OpenApiSpecVersion version) { }
     }
@@ -2028,11 +2028,11 @@ namespace Microsoft.OpenApi.Writers
         public override void WriteEndArray() { }
         public override void WriteEndObject() { }
         public override void WriteNull() { }
-        public override void WritePropertyName(string? name) { }
+        public override void WritePropertyName(string name) { }
         public override void WriteRaw(string value) { }
         public override void WriteStartArray() { }
         public override void WriteStartObject() { }
-        public override void WriteValue(string? value) { }
+        public override void WriteValue(string value) { }
         protected override void WriteValueSeparator() { }
     }
     public sealed class Scope