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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 open(cls, filename, crs=None):
 """Creates a FileCollection from a file in disk. Parameters filename : str Path of the file to read. crs : CRS overrides the crs of the collection, this funtion will not reprojects """

        with fiona.Env():
            with fiona.open(filename, 'r') as source:
                original_crs = CRS(source.crs)
                schema = source.schema
                length = len(source)
        crs = crs or original_crs
        ret_val = cls(filename, crs, schema, length)
        return ret_val