A method that returns the method signature for this function. Each function signature includes a list of parameters to which the analyzer can compare a function call with provided arguments to determine if that function call is a match for the function signature.

IMPORTANT: For now, each function expression builder should have only one function signature. Also, for any function signature, required arguments must always come before optional ones.

This function rearranges the arguments provided during function invocation in positional order according to the function signature. This method will fill in the default values if optional parameters do not have their values specified. Any function which supports named arguments will have this routine invoked, even if no named arguments are present in the argument list. This is done to eliminate constructor overloads in some methods which use them for default values prior to the implementation of the named argument framework. This function will also check if the number of arguments are correct. If that is not the case, then an error will be thrown.

IMPORTANT: This method will be called before the FunctionBuilderBase.build method is invoked. It is guaranteed that the expressions provided to the FunctionBuilderBase.build functions forms a valid set of argument expressions that can be used in the construction of the function expression.