Ability to specify block size in block upload

Removed hard coded blocksize value in the "BlockUploadStream" class. 
Introduced a default value, but added it as a parameter that can be passed in so that block size can be specified when performing an Upload.

Author: Beemo123

canopen/sdo/client.py

@@ -1,5 +1,6 @@
 import io
-import logging
+import
+ logging
 import queue
 import struct
 import time
@@ -169,7 +170,7 @@ def download(
             fp.write(data)
 
     def open(self, index, subindex=0, mode="rb", encoding="ascii",
-             buffering=1024, size=None, block_transfer=False, force_segment=False, request_crc_support=True):
+             buffering=1024, size=None, block_transfer=False, force_segment=False, request_crc_support=True, blksize=127):
         """Open the data stream as a file like object.
 
         :param int index:
@@ -201,14 +202,16 @@ def open(self, index, subindex=0, mode="rb", encoding="ascii",
             Force use of segmented download regardless of data size.
         :param bool request_crc_support:
             If crc calculation should be requested when using block transfer
+        :param int blksize:
+            Size of block in number of segments. Default is 127.
 
         :returns:
             A file like object.
         """
         buffer_size = buffering if buffering > 1 else io.DEFAULT_BUFFER_SIZE
         if "r" in mode:
             if block_transfer:
-                raw_stream = BlockUploadStream(self, index, subindex, request_crc_support=request_crc_support)
+                raw_stream = BlockUploadStream(self, index, subindex, request_crc_support=request_crc_support, blksize=blksize)
             else:
                 raw_stream = ReadableStream(self, index, subindex)
             if buffering:
@@ -463,11 +466,9 @@ class BlockUploadStream(io.RawIOBase):
     #: Total size of data or ``None`` if not specified
     size = None
 
-    blksize = 127
-
     crc_supported = False
 
-    def __init__(self, sdo_client, index, subindex=0, request_crc_support=True):
+    def __init__(self, sdo_client, index, subindex=0, request_crc_support=True, blksize=127):
         """
         :param canopen.sdo.SdoClient sdo_client:
             The SDO client to use for reading.
@@ -477,14 +478,17 @@ def __init__(self, sdo_client, index, subindex=0, request_crc_support=True):
             Object dictionary sub-index to read from.
         :param bool request_crc_support:
             If crc calculation should be requested when using block transfer
+        :param int blksize:
+            Size of block in number of segments. Default is 127.
         """
         self._done = False
         self.sdo_client = sdo_client
         self.pos = 0
         self._crc = sdo_client.crc_cls()
         self._server_crc = None
         self._ackseq = 0
-        self._error = False
+        self._error = False        
+        self.blksize = blksize
 
         logger.debug("Reading 0x%04X:%02X from node %d", index, subindex,
                      sdo_client.rx_cobid - 0x600)