DeflateStream is an overridden procedure that implements the abstract virtual method declared in the ancestor class. DeflateStream provides stream-based decompression using the ZLib DEFLATE algorithm defined in RFC 1951. 

AStream is the stream with the uncompressed values for the operation. 

ALevel indicates desired compression level for the operation. 

AOutStream is the optional outstream stream for the values after compression using the defalte algorithm. AOutStream is cleared prior to writing the compressed values from the deflate algorithm to the stream. When AOutStream is omitted, the stream in AStream is cleared and reused for the output from the compression algorithm. 

DeflateStream can raise an EIdCompressorInitFailure exception if the ZLib library cannot be initialized using the parameters provided to the method. DeflateStream may also raise an EIdCompressionError exception during the deflate operation.