How to use the xblock.fields.Scope function in XBlock

import inspect
import random
import string  # pylint: disable=W0402
import time

from xblock.core import XBlock
from xblock.fields import Integer, Scope, String, Any, Boolean, Dict
from xblock.run_script import run_script
from xblock.fragment import Fragment


class ProblemBlock(XBlock):
    """A generalized container of InputBlocks and Checkers.

    """
    script = String(help="Python code to compute values", scope=Scope.content, default="")
    seed = Integer(help="Random seed for this student", scope=Scope.user_state, default=0)
    problem_attempted = Boolean(help="Has the student attempted this problem?", scope=Scope.user_state, default=False)
    has_children = True

    @classmethod
    def parse_xml(cls, node, runtime, keys):
        block = runtime.construct_xblock_from_class(cls, keys)

        # Find 

def _key(self, block, name):
        """
        Resolves `name` to a key, in the following form:

        KeyValueStore.Key(
            scope=field.scope,
            user_id=student_id,
            block_scope_id=block_id,
            field_name=name,
            block_family=block.entry_point,
        )
        """
        field = self._getfield(block, name)
        if field.scope in (Scope.children, Scope.parent):
            block_id = block.scope_ids.usage_id
            user_id = None
        else:
            block_scope = field.scope.block

            if block_scope == BlockScope.ALL:
                block_id = None
            elif block_scope == BlockScope.USAGE:
                block_id = block.scope_ids.usage_id
            elif block_scope == BlockScope.DEFINITION:
                block_id = block.scope_ids.def_id
            elif block_scope == BlockScope.TYPE:
                block_id = block.scope_ids.block_type

            if field.scope.user == UserScope.ONE:
                user_id = block.scope_ids.user_id

scope=Scope.user_state,
        default=0
    )
    weight = Float(
        default=1,
        scope=Scope.settings
    )
    has_score = Boolean(
        display_name=_("Scored"),
        help=_("Select False if this component will not receive a numerical score from the Scorm"),
        default=True,
        scope=Scope.settings
    )
    icon_class = String(
        default="video",
        scope=Scope.settings,
    )
    width = Integer(
        display_name=_("Display Width (px)"),
        help=_('Width of iframe, if empty, the default 100%'),
        scope=Scope.settings
    )
    height = Integer(
        display_name=_("Display Height (px)"),
        help=_('Height of iframe'),
        default=450,
        scope=Scope.settings
    )

    has_author_view = True

    def resource_string(self, path):

class ThumbsBlock(XBlock):
    """
    An XBlock with thumbs-up/thumbs-down voting.

    Vote totals are stored for all students to see.  Each student is recorded
    as has-voted or not.

    This demonstrates multiple data scopes and ajax handlers.

    """

    upvotes = Integer(help="Number of up votes", default=0, scope=Scope.user_state_summary)
    downvotes = Integer(help="Number of down votes", default=0, scope=Scope.user_state_summary)
    voted = Boolean(help="Has this student voted?", default=False, scope=Scope.user_state)

    def student_view(self, context=None):  # pylint: disable=W0613
        """
        Create a fragment used to display the XBlock to a student.
        `context` is a dictionary used to configure the display (unused)

        Returns a `Fragment` object specifying the HTML, CSS, and JavaScript
        to display.
        """

        # Load the HTML fragment from within the package and fill in the template
        html_str = pkg_resources.resource_string(__name__, "static/html/thumbs.html")
        frag = Fragment(unicode(html_str).format(self=self))

        # Load the CSS and JavaScript fragments from within the package
        css_str = pkg_resources.resource_string(__name__, "static/css/thumbs.css")

{'children': [frag.body_html() for frag in child_frags]}))
        return result


class HtmlBlock(XBlock):
    """An XBlock which presents a single block of HTML.

    See xmodule.html_module.HtmlModule in
    https://github.com/edx/edx-platform.
    """

    content = String(
        display_name='HTML Text',
        help='A block of HTML text',
        default='HTML text',
        scope=Scope.content)

    def student_view(self, context=None):
        frag = Fragment()
        frag.add_content(self.content)
        return frag

    @classmethod
    def parse_xml(cls, node, runtime, keys, id_generator):
        block = runtime.construct_xblock_from_class(cls, keys)

        block.content = unicode(node.text or u'')
        for child in node:
            block.content += etree.tostring(
                child,
                # Store the content with HTML rather than  XML structure so as
                # to correctly handle edge cases such as '<br>' (not '<br>')