CelMacroExpander

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
@Immutable
public interface CelMacroExpander
```
Converts the target and arguments of a function call that matches a macro.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.util.Optional<CelExpr>`	`expandMacro(CelMacroExprFactory exprFactory, CelExpr target, com.google.common.collect.ImmutableList<CelExpr> arguments)`	Converts a call and its associated arguments into a new CEL AST.

- Method Detail
  - expandMacro
```
java.util.Optional<CelExpr> expandMacro(CelMacroExprFactory exprFactory,
                                        CelExpr target,
                                        com.google.common.collect.ImmutableList<CelExpr> arguments)
```
    Converts a call and its associated arguments into a new CEL AST.
    
    Parameters:
    
    exprFactory - Expression factory to assist with expansion of this macro.
    
    target - Target expression which the macro is being invoked on. Default instance of Expr is provided instead for global macros.
    
    arguments - Arguments of the call
    
    Returns:
    
    A newly generated CEL AST. Implementations may return Optional.Empty instead to signal that an expansion is not needed.