Tidy package imports (#34)

Author: odow

src/MathOptSymbolicAD.jl

@@ -6,13 +6,10 @@
 
 module MathOptSymbolicAD
 
-import Base.Meta: isexpr
-import MathOptInterface
+import MathOptInterface as MOI
 import SparseArrays
 import Symbolics
 
-const MOI = MathOptInterface
-
 abstract type AbstractSymbolicBackend <:
               MOI.Nonlinear.AbstractAutomaticDifferentiation end
 

src/nonlinear_oracle.jl

@@ -173,7 +173,7 @@ Parse `expr` into `f` and return a `_Node`.
     This function gets called recursively.
 """
 function _Node(f::_Function, expr::Expr)
-    @assert isexpr(expr, :call)
+    @assert Meta.isexpr(expr, :call)
     # Performance optimization: most calls will be unary or binary
     # operators. Therefore, we can specialize an if-statement to handle the
     # common cases without needing to splat.