Question #$10$ successors$($file$\_$name$)$

Returns a dictionary whose keys are included words $($as is$),$ and values are lists of unique successors to those words. The first word of the txt file is always a successor to $".".$ Be careful with punctuation. You can assume the text in the txt file does not contain any contraction words $($isn$$t$,$ don$$t$,$ I$$m$,$ etc$)$ but you cannot make assumptions about the spacing or the presence of non$-$alphanumerical characters. The starter code already contains the code to read the txt file, just make sure the file is in the same directory as your $.$py file. You must write your code after the file has been read to process the contents.