isGenericS4: Checks if a function is a S4 generic function
Description
Checks if a function is a S4 generic function.
Usage
# S3 method for default
isGenericS4(fcn, envir=parent.frame(), ...)
Value
Returns TRUE if a generic S4 function, otherwise FALSE.
Details
A function is considered to be a generic S4 function if its
  body, that is the source code, contains the regular pattern
  "standardGeneric".