Merge pull request #2158 from SciML/myb/dep

Fix the deprecation warning

Author: YingboMa

docs/src/basics/Linearization.md

@@ -50,6 +50,7 @@ The operating point to linearize around can be specified with the keyword argume
 If linearization is to be performed around multiple operating points, the simplification of the system has to be carried out a single time only. To facilitate this, the lower-level function [`ModelingToolkit.linearization_function`](@ref) is available. This function further allows you to obtain separate Jacobians for the differential and algebraic parts of the model. For ODE models without algebraic equations, the statespace representation above is available from the output of `linearization_function` as `A, B, C, D = f_x, f_u, h_x, h_u`.
 
 ## Symbolic linearization
+
 The function [`ModelingToolkit.linearize_symbolic`](@ref) works simiar to [`ModelingToolkit.linearize`](@ref) but returns symbolic rather than numeric Jacobians. Symbolic linearization have several limitations and no all systems that can be linearized numerically can be linearized symbolically.
 
 ## Input derivatives

src/systems/connectors.jl

@@ -169,13 +169,15 @@ end
 
 "Return true if the system is a 3D multibody frame, otherwise return false."
 function isframe(sys)
-    sys.metadata isa Dict || return false
-    get(sys.metadata, :frame, false)
+    (has_metadata(sys) && (md = get_metadata(sys)) isa Dict) || return false
+    get(md, :frame, false)
 end
 
 "Return orienation object of a multibody frame."
 function ori(sys)
-    if sys.metadata isa Dict && (O = get(sys.metadata, :orientation, nothing)) !== nothing
+    @assert has_metadata(sys)
+    md = get_metadata(sys)
+    if md isa Dict && (O = get(md, :orientation, nothing)) !== nothing
         return O
     else
         error("System $(sys.name) does not have an orientation object.")