code: @Nullable
      public static XMethod getXMethod(String slashedClassName, String methodName, String methodSig) {
          final XClass xClass = getXClass(slashedClassName);
          return getXMethod(xClass, methodName, methodSig);
      }
docs: Looks for the method up the class hierarchy.
  
  @param slashedClassName
  the class slashed name where to look for the method
  @param methodName
  the name of the method to look for
  @param methodSig
  the signature of the method to look for
  @return the method