Clone returns a deep copy of the base function table.

ToFunction takes in a function with any arguments and attempts to convert it to a functions.Function type.

Function contains the FHIRPathFunction, along with metadata.

FHIRPathFunc is the common abstraction for all function types supported by FHIRPath.

FunctionTable is the data structure used to store valid FHIRPath functions, and maps their case-sensitive names.