How to use the beancount.core.realization.realize function in beancount

# Compute the list of entries for the opening balances sheet.
        self.opening_entries = (self.entries[:self.begin_index]
                                if self.begin_index is not None
                                else [])

        # Compute the list of entries that includes transfer entries of the
        # income/expenses amounts to the balance sheet's equity (as "net
        # income"). This is used to render the end-period balance sheet, with
        # the current period's net income, closing the period.
        self.closing_entries = summarize.cap_opt(self.entries, options_map)

        # Realize the three sets of entries.
        account_types = options.get_account_types(options_map)
        with misc_utils.log_time('realize_opening', logging.info):
            self.opening_real_accounts = realization.realize(self.opening_entries,
                                                             account_types)

        with misc_utils.log_time('realize', logging.info):
            self.real_accounts = realization.realize(self.entries,
                                                     account_types)

        with misc_utils.log_time('realize_closing', logging.info):
            self.closing_real_accounts = realization.realize(self.closing_entries,
                                                             account_types)

        assert self.real_accounts is not None
        assert self.closing_real_accounts is not None

def merge_postings(entries, accounts):
    """Merge all the postings from the given account names.

    Args:
      entries: A list of directives.
      accounts: A list of account strings to get the balances for.
    Yields:
      A list of TxnPosting's for all the accounts, in sorted order.
    """
    real_root = realization.realize(entries)
    merged_postings = []
    for account in accounts:
        real_account = realization.get(real_root, account)
        if real_account is None:
            continue
        merged_postings.extend(txn_posting
                               for txn_posting in real_account.txn_postings
                               if isinstance(txn_posting, data.TxnPosting))
    merged_postings.sort(key=lambda txn_posting: txn_posting.txn.date)
    return merged_postings

# income"). This is used to render the end-period balance sheet, with
        # the current period's net income, closing the period.
        self.closing_entries = summarize.cap_opt(self.entries, options_map)

        # Realize the three sets of entries.
        account_types = options.get_account_types(options_map)
        with misc_utils.log_time('realize_opening', logging.info):
            self.opening_real_accounts = realization.realize(self.opening_entries,
                                                             account_types)

        with misc_utils.log_time('realize', logging.info):
            self.real_accounts = realization.realize(self.entries,
                                                     account_types)

        with misc_utils.log_time('realize_closing', logging.info):
            self.closing_real_accounts = realization.realize(self.closing_entries,
                                                             account_types)

        assert self.real_accounts is not None
        assert self.closing_real_accounts is not None

def _apply_filters(self):
        self.entries = self.all_entries

        for filter in self.filters.values():
            self.entries = filter.apply(self.entries, self.options)

        self.closing_entries = summarize.cap_opt(self.entries, self.options)
        self.root_account = realization.realize(self.entries,
                                                self.account_types)

self.title = self.options['title']
        if self.options['render_commas']:
            self.format_string = '{:,f}'
            self.default_format_string = '{:,.2f}'
        else:
            self.format_string = '{:f}'
            self.default_format_string = '{:.2f}'
        self.dcontext = self.options['dcontext']

        self.active_years = list(getters.get_active_years(self.all_entries))
        self.active_tags = list(getters.get_all_tags(self.all_entries))
        self.active_payees = list(getters.get_all_payees(self.all_entries))

        self.queries = self._entries_filter_type(self.all_entries, Query)

        self.all_root_account = realization.realize(self.all_entries,
                                                    self.account_types)
        self.all_accounts = self._all_accounts()
        self.all_accounts_leaf_only = self._all_accounts(leaf_only=True)

        self._apply_filters()

def create_report(entries, options_map):
    real_root = realization.realize(entries)

    # Find the institutions from the data.
    groups, ignored_accounts = find_institutions(entries, options_map)

    # List all the asset accounts which aren't included in the report.
    oc_map = getters.get_account_open_close(entries)
    open_map = {acc: open_entry for acc, (open_entry, _) in oc_map.items()}
    for acc in sorted(ignored_accounts):
        logging.info("Ignored account: %s", acc)

    # Gather missing fields and create a report object.
    institutions = []
    for name, accounts in sorted(groups.items()):
        # Get the institution fields, which is the union of the fields for all
        # the accounts with the institution fields.
        institution_accounts = [acc for acc in accounts

# income"). This is used to render the end-period balance sheet, with
        # the current period's net income, closing the period.
        self.closing_entries = summarize.cap_opt(self.entries, options_map)

        # Realize the three sets of entries.
        account_types = options.get_account_types(options_map)
        with misc_utils.log_time('realize_opening', logging.info):
            self.opening_real_accounts = realization.realize(self.opening_entries,
                                                             account_types)

        with misc_utils.log_time('realize', logging.info):
            self.real_accounts = realization.realize(self.entries,
                                                     account_types)

        with misc_utils.log_time('realize_closing', logging.info):
            self.closing_real_accounts = realization.realize(self.closing_entries,
                                                             account_types)

        assert self.real_accounts is not None
        assert self.closing_real_accounts is not None

def load_file(self):
        """Load the main file and all included files and set attributes."""
        # use the internal function to disable cache
        if not self._is_encrypted:
            # pylint: disable=protected-access
            self.all_entries, self.errors, self.options = loader._load(
                [(self.beancount_file_path, True)], None, None, None
            )
        else:
            self.all_entries, self.errors, self.options = loader.load_file(
                self.beancount_file_path
            )

        self.account_types = get_account_types(self.options)
        self.price_map = prices.build_price_map(self.all_entries)
        self.all_root_account = realization.realize(
            self.all_entries, self.account_types
        )

        entries_by_type = collections.defaultdict(list)
        for entry in self.all_entries:
            entries_by_type[type(entry)].append(entry)
        self.all_entries_by_type = entries_by_type

        self.accounts = _AccountDict()
        for entry in entries_by_type[Open]:
            self.accounts.setdefault(entry.account).meta = entry.meta
        for entry in entries_by_type[Close]:
            self.accounts.setdefault(entry.account).close_date = entry.date

        self.fava_options, errors = parse_options(entries_by_type[Custom])
        self.errors.extend(errors)

else [])

        # Compute the list of entries that includes transfer entries of the
        # income/expenses amounts to the balance sheet's equity (as "net
        # income"). This is used to render the end-period balance sheet, with
        # the current period's net income, closing the period.
        self.closing_entries = summarize.cap_opt(self.entries, options_map)

        # Realize the three sets of entries.
        account_types = options.get_account_types(options_map)
        with misc_utils.log_time('realize_opening', logging.info):
            self.opening_real_accounts = realization.realize(self.opening_entries,
                                                             account_types)

        with misc_utils.log_time('realize', logging.info):
            self.real_accounts = realization.realize(self.entries,
                                                     account_types)

        with misc_utils.log_time('realize_closing', logging.info):
            self.closing_real_accounts = realization.realize(self.closing_entries,
                                                             account_types)

        assert self.real_accounts is not None
        assert self.closing_real_accounts is not None

holdings. If left unspecified, we use the latest price information.
    Returns:
      A list of dicts, with the following fields:
    """
    # Remove the entries inserted by unrealized gains/losses. Those entries do
    # affect asset accounts, and we don't want them to appear in holdings.
    #
    # Note: Perhaps it would make sense to generalize this concept of "inserted
    # unrealized gains."
    simple_entries = [entry
                      for entry in entries
                      if (not isinstance(entry, data.Transaction) or
                          entry.flag != flags.FLAG_UNREALIZED)]

    # Realize the accounts into a tree (because we want the positions by-account).
    root_account = realization.realize(simple_entries)

    # For each account, look at the list of positions and build a list.
    holdings = []
    for real_account in sorted(list(realization.iter_children(root_account)),
                               key=lambda ra: ra.account):

        if included_account_types:
            # Skip accounts of invalid types, we only want to reflect the requested
            # account types, typically assets and liabilities.
            account_type = account_types.get_account_type(real_account.account)
            if account_type not in included_account_types:
                continue

        for pos in real_account.balance.get_positions():
            if pos.cost is not None:
                # Get price information if we have a price_map.