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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_output(a1_text, a2_text, sentence_segmentations):
 """Parses the output of the TEES reader and returns a networkx graph with the event information. Parameters a1_text : str Contents of the TEES a1 output, specifying the entities a1_text : str Contents of the TEES a2 output, specifying the event graph sentence_segmentations : str Concents of the TEES sentence segmentation output XML Returns ------- events : networkx.DiGraph networkx graph with the entities, events, and relationship between extracted by TEES """


    # Parse the sentence segmentation document
    tees_sentences = TEESSentences(sentence_segmentations)

    # Parse the a1 (entities) file
    entities = parse_a1(a1_text)

    # Parse the a2 (events) file
    events = parse_a2(a2_text, entities, tees_sentences)

    return events