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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 encode_sourcemap(filename, mappings, sources, names=[]):
 """ Take a filename, mappings and names produced from the write function and sources. As the write function currently does not handle the tracking of source filenames, the sources should be a list of one element with the original filename. Arguments filename The target filename that the stream was or to be written to. The stream being the argument that was supplied to the write function mappings The raw unencoded mappings produced by write, which is returned as its second element. sources List of original source filenames. When used in conjunction with the above write function, it should be a list of one item, being the path to the original filename. names The list of original names generated by write, which is returned as its first element. Returns a dict which can be JSON encoded into a sourcemap file. Example usage: """


    return {
        "version": 3,
        "sources": sources,
        "names": names,
        "mappings": encode_mappings(mappings),
        "file": filename,
    }