def __init__(<EOL>self,<EOL>steem_instance=None,<EOL>mode="<STR_LIT>"<EOL>):
if not steem_instance:<EOL><INDENT>steem_instance = stm.Steem()<EOL><DEDENT>self.steem = steem_instance<EOL>if mode == "<STR_LIT>":<EOL><INDENT>self.mode = '<STR_LIT>'<EOL><DEDENT>elif mode == "<STR_LIT>":<EOL><INDENT>self.mode = "<STR_LIT>"<EOL><DEDENT>else:<EOL><INDENT>raise ValueError("<STR_LIT>")<EOL><DEDENT>
This class allows to access the blockchain and read data
            from it

            :param Steem steem: Steem() instance to use when accesing a RPC
            :param str mode: (default) Irreversible block
                    (``irreversible``) or actual head block (``head``)