get File Descriptor By Id
Returns a RainbowFileDescriptor if found in local list
Return
a RainbowFileDescriptor if found or null
Parameters
file Descriptor Id
String the unique identifier of the RainbowFileDescriptor
Returns a RainbowFileDescriptor if found in local list
a RainbowFileDescriptor if found or null
String the unique identifier of the RainbowFileDescriptor