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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 pack_gzip(params, ctxt, scope, stream, coord):
 """``PackGZip`` - Concats the build output of all params and gzips the resulting data, returning a char array. Example: :: """

    if len(params) == 0:
        raise errors.InvalidArguments(coord, "{} args".format(len(params)), "at least one argument")
    
    built = utils.binary("")
    for param in params:
        if isinstance(param, pfp.fields.Field):
            built += param._pfp__build()
        else:
            built += param
    
    return zlib.compress(built)