Return chunk_size of bytes, starting from self.pos, from self.content.

def read(self, chunk_size=None):
        """
        Return chunk_size of bytes, starting from self.pos, from self.content.
        """
        if chunk_size:
            data = self.content[self.pos:self.pos + chunk_size]
            self.pos += len(data)
            return data
        else:
            return self.content