Function _copy_source

Create a source in a graph based on a Tensor from a different graph. This function creates a placeholder analog of `s` in a graph with the following behavior: 1) If s is a captured Tensor or Variable and handle_captures is set to True, simply capture it in the new graph as well. 2) I

(s, graph, op_map, handle_captures, inverse_captures,
                 base_graph)