How to use the pyflakes.checker.Checker function in pyflakes

else:
            line = text.splitlines()[-1]

            if offset is not None:
                offset = offset - (len(text) - len(line))

            print >> sys.stderr, '%s:%d: %s' % (filename, lineno, msg)
            print >> sys.stderr, line

            if offset is not None:
                print >> sys.stderr, " " * offset, "^"

        return 1
    else:
        # Okay, it's syntactically valid.  Now check it.
        w = checker.Checker(tree, filename)
        lines = codeString.split('\n')
        messages = [message for message in w.messages
                    if lines[message.lineno - 1].find('pyflakes:ignore') < 0]
        messages.sort(lambda a, b: cmp(a.lineno, b.lineno))
        for warning in messages:
            print warning
        return len(messages)

# If there's an encoding problem with the file, the text is None.
        if text is None:
            # Avoid using msg, since for the only known case, it contains a
            # bogus message that claims the encoding the file declared was
            # unknown.
            reporter.unexpectedError(filename, 'problem decoding source')
        else:
            reporter.syntaxError(filename, msg, lineno, offset, text)
        return 1
    except Exception:
        reporter.unexpectedError(filename, 'problem decoding source')
        return 1
    else:
        # Okay, it's syntactically valid.  Now check it.
        lines = codeString.splitlines()
        warnings = Checker(tree, filename)
        warnings.messages.sort(key=lambda m: m.lineno)
        real_messages = []
        for m in warnings.messages:
            line = lines[m.lineno - 1]
            if 'pyflakes:ignore' in line.rsplit('#', 1)[-1]:
                # ignore lines with pyflakes:ignore
                pass
            else:
                real_messages.append(m)
                reporter.flake(m)
        return len(real_messages)

def run(path, code=None, params=None, **meta):
        """ Pyflake code checking.

        :return list: List of errors.

        """
        import _ast

        builtins = params.get("builtins", "")

        if builtins:
            builtins = builtins.split(",")

        errors = []
        tree = compile(code, path, "exec", _ast.PyCF_ONLY_AST)
        w = checker.Checker(tree, path, builtins=builtins)
        w.messages = sorted(w.messages, key=lambda m: m.lineno)
        for w in w.messages:
            errors.append(dict(
                lnum=w.lineno,
                text=w.message % w.message_args,
            ))
        return errors

_ast.PyCF_ONLY_AST)
        except SyntaxError as value:
            msg = '[pyFlakes] %s' % value.args[0]
            (lineno, offset, text) = value.lineno - 1, value.offset, value.text
            # If there's an encoding problem with the file, the text is None
            if text is None:
                # Avoid using msg, since for the only known case, it
                # contains a bogus message that claims the encoding the
                # file declared was unknown.s
                _logger().warning("[SyntaxError] %s: problem decoding source",
                                  path)
            else:
                ret_val.append((msg, ERROR, lineno))
        else:
            # Okay, it's syntactically valid.  Now check it.
            w = checker.Checker(tree, os.path.split(path)[1])
            w.messages.sort(key=lambda m: m.lineno)
            for message in w.messages:
                msg = "[pyFlakes] %s" % str(message).split(':')[-1].strip()
                line = message.lineno - 1
                status = WARNING \
                    if message.__class__ not in PYFLAKES_ERROR_MESSAGES \
                    else ERROR
                ret_val.append((msg, status, line))
    prev_results = ret_val
    return ret_val

(lineno, offset, text) = value.lineno, value.offset, value.text

        # If there's an encoding problem with the file, the text is None.
        if text is None:
            # Avoid using msg, since for the only known case, it contains a
            # bogus message that claims the encoding the file declared was
            # unknown.
            reporter.unexpectedError(filename, 'problem decoding source')
        else:
            reporter.syntaxError(filename, msg, lineno, offset, text)
        return 1
    except Exception:
        reporter.unexpectedError(filename, 'problem decoding source')
        return 1
    # Okay, it's syntactically valid.  Now check it.
    w = checker.Checker(tree, filename)
    w.messages.sort(key=lambda m: m.lineno)
    for warning in w.messages:
        reporter.flake(warning)
    return len(w.messages)

msg = value.args[0]
        lineno = value.lineno
        # If there's an encoding problem with the file, the text is None.
        if value.text is None:
            # Avoid using msg, since for the only known case, it contains a
            # bogus message that claims the encoding the file declared was
            # unknown.
            msg = "Problem decoding source"
            lineno = 1
        error = Message(filename, lineno)
        error.message = msg + "%s"
        error.message_args = ""
        return [error]
    else:
        # Okay, it's syntactically valid.  Now check it.
        w = Checker(tree, filename)
        return w.messages

(lineno, offset, text) = value.lineno, value.offset, value.text

        # If there's an encoding problem with the file, the text is None.
        if text is None:
            # Avoid using msg, since for the only known case, it contains a
            # bogus message that claims the encoding the file declared was
            # unknown.
            reporter.unexpectedError(filename, 'problem decoding source')
        else:
            reporter.syntaxError(filename, msg, lineno, offset, text)
        return 1
    except Exception:
        reporter.unexpectedError(filename, 'problem decoding source')
        return 1
    # Okay, it's syntactically valid.  Now check it.
    w = checker.Checker(tree, filename)
    w.messages.sort(key=lambda m: m.lineno)
    for warning in w.messages:
        reporter.flake(warning)
    return len(w.messages)

# If there's an encoding problem with the file, the text is None.
        if text is None:
            # Avoid using msg, since for the only known case, it contains a
            # bogus message that claims the encoding the file declared was
            # unknown.
            reporter.unexpectedError(filename, 'problem decoding source')
        else:
            reporter.syntaxError(filename, msg, lineno, offset, text)
        return 1
    except Exception:
        reporter.unexpectedError(filename, 'problem decoding source')
        return 1
    # Okay, it's syntactically valid.  Now check it.
    file_tokens = checker.make_tokens(codeString)
    w = checker.Checker(tree, file_tokens=file_tokens, filename=filename)
    w.messages.sort(key=lambda m: m.lineno)
    for warning in w.messages:
        reporter.flake(warning)
    return len(w.messages)

while endcol < len(line) and line[endcol] != '\n':
                endcol += 1
            if endcol == len(line):
                endcol += 1
            if col >= len(line):
                # Handle col == len(line) and also a bug where the col is very large.
                line = line + ' '*(col - len(line) + 1)
            while col > 0 and line[col] != '\n':
                col -= 1

            for c in range(col + col_offset, endcol + col_offset):
                yield (row, c, m.message % m.message_args, m)
            return

        try:
            checker = Checker(tree, builtins=defined_names)
        except RecursionError:
            return
        messages = checker.messages
        for m in messages:
            if isinstance(m, skip):
                continue
            row = m.lineno - 1
            col = m.col
            msg = m.message % m.message_args

            endcol = col
            if isinstance(m, (UndefinedName, UnusedVariable)):
                endcol = col + len(m.message_args[0])
            else:
                # Highlight the whole line
                line = code.splitlines()[row]