The offset in source where the error was detected.
A zero-based offset into the source that marks the format error causing
this exception to be created. If
source is a string, this should be a
string index in the range
0 <= offset <= source.length.
If input is a string, the toString method may represent this offset as a line and character position. The offset should be inside the string, or at the end of the string.
May be omitted. If present, source should also be present if possible.
final int? offset;