Create csvparser.py

I am adding the CSV parser python code.
it works with basic CSV files.

Author: saravana87

app/backend/prepdocslib/csvparser.py

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+import csv
+from typing import IO, AsyncGenerator
+from .page import Page
+from .parser import Parser
+
+
+class CsvParser(Parser):
+    """
+    Concrete parser that can parse CSV into Page objects. Each row becomes a Page object.
+    """
+
+    async def parse(self, content: IO) -> AsyncGenerator[Page, None]:
+        # Ensure the file is read in text mode
+        text_content = content.read().decode('utf-8')  # Decode bytes to string if opened in binary mode
+        reader = csv.reader(text_content.splitlines())  # Create CSV reader from text lines
+        offset = 0
+        for i, row in enumerate(reader):
+            page_text = ",".join(row)  # Combine CSV row elements back to a string
+            yield Page(i, offset, page_text)
+            offset += len(page_text) + 1  # Add 1 for the newline character or comma