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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 getKeyName(username, date, blob_key):
 """Returns the internal key for a particular item in the database. Our items are stored with keys of the form 'user/date/blob_key' ('/' is not the real separator, but __SEP is). Args: username: The given user's e-mail address. date: A datetime object representing the date and time that an input file was uploaded to this app. blob_key: The blob key corresponding to the location of the input file in the Blobstore. Returns: The internal key for the item specified by (username, date, blob_key). """


    sep = FileMetadata.__SEP
    return str(username + sep + str(date) + sep + blob_key)