[SONIC_SFP] adding abstract methods for reading and writing the eepro…

…m address space within platform api (sonic-net#126)

* [sonic_sfp] adding abstract methods for platform api's

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>

sonic_platform_base/sfp_base.py

@@ -356,3 +356,39 @@ def set_power_override(self, power_override, power_set):
             False if not
         """
         raise NotImplementedError
+
+    def read_eeprom(self, offset, num_bytes):
+        """
+        read eeprom specfic bytes beginning from a random offset with size as num_bytes
+
+        Args:
+             offset :
+                     Integer, the offset from which the read transaction will start
+             num_bytes:
+                     Integer, the number of bytes to be read
+
+        Returns:
+            bytearray, if raw sequence of bytes are read correctly from the offset of size num_bytes
+            None, if the read_eeprom fails
+        """
+        raise NotImplementedError
+
+    def write_eeprom(self, offset, num_bytes, write_buffer):
+        """
+        write eeprom specfic bytes beginning from a random offset with size as num_bytes 
+        and write_buffer as the required bytes
+
+        Args:
+             offset :
+                     Integer, the offset from which the read transaction will start
+             num_bytes:
+                     Integer, the number of bytes to be written
+             write_buffer:
+                     bytearray, raw bytes buffer which is to be written beginning at the offset
+
+        Returns:
+            a Boolean, true if the write succeeded and false if it did not succeed.
+        """
+        raise NotImplementedError
+
+