def append_blob_from_stream(<EOL>self, container_name, blob_name, stream, count=None,<EOL>validate_content=False, maxsize_condition=None, progress_callback=None, <EOL>lease_id=None, timeout=None):
_validate_not_none('<STR_LIT>', container_name)<EOL>_validate_not_none('<STR_LIT>', blob_name)<EOL>_validate_not_none('<STR_LIT>', stream)<EOL>_validate_encryption_unsupported(self.require_encryption, self.key_encryption_key)<EOL>_upload_blob_chunks(<EOL>blob_service=self,<EOL>container_name=container_name,<EOL>blob_name=blob_name,<EOL>blob_size=count,<EOL>block_size=self.MAX_BLOCK_SIZE,<EOL>stream=stream,<EOL>max_connections=<NUM_LIT:1>, <EOL>progress_callback=progress_callback,<EOL>validate_content=validate_content,<EOL>lease_id=lease_id,<EOL>uploader_class=_AppendBlobChunkUploader,<EOL>maxsize_condition=maxsize_condition,<EOL>timeout=timeout<EOL>)<EOL>
Appends to the content of an existing blob from a file/stream, with
automatic chunking and progress notifications.

:param str container_name:
    Name of existing container.
:param str blob_name:
    Name of blob to create or update.
:param io.IOBase stream:
    Opened stream to upload as the blob content.
:param int count:
    Number of bytes to read from the stream. This is optional, but
    should be supplied for optimal performance.
:param bool validate_content:
    If true, calculates an MD5 hash for each chunk of the blob. The storage 
    service checks the hash of the content that has arrived with the hash 
    that was sent. This is primarily valuable for detecting bitflips on 
    the wire if using http instead of https as https (the default) will 
    already validate. Note that this MD5 hash is not stored with the 
    blob.
:param int maxsize_condition:
    Conditional header. The max length in bytes permitted for
    the append blob. If the Append Block operation would cause the blob
    to exceed that limit or if the blob size is already greater than the
    value specified in this header, the request will fail with
    MaxBlobSizeConditionNotMet error (HTTP status code 412 - Precondition Failed).
:param progress_callback:
    Callback for progress with signature function(current, total) where
    current is the number of bytes transfered so far, and total is the
    size of the blob, or None if the total size is unknown.
:type progress_callback: callback function in format of func(current, total)
:param str lease_id:
    Required if the blob has an active lease.
:param int timeout:
    The timeout parameter is expressed in seconds. This method may make 
    multiple calls to the Azure service and the timeout will apply to 
    each call individually.