ref_source
  
  Description:
  public Source? 
ref_source (
string uid)
  
 
  
    Looks up an Source in this by its unique
      identifier string.
    The returned Source is referenced for thread-safety and must be unreferenced with
      unref when finished with it.
    Parameters:
    
      
        | this | an SourceRegistry | 
      
        | uid | a unique identifier string | 
    
    Returns:
    
      
        | an Source, or nullif no match was found |