python/mxnet/attribute.py

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"""Attribute scoping support for symbolic API."""
import contextvars
from collections import defaultdict

from .base import string_types

class AttrScope:
    """Attribute manager for scoping.

    User can also inherit this object to change naming behavior.

    Parameters
    ----------
    kwargs
        The attributes to set for all symbol creations in the scope.
    """
    _subgraph_names = defaultdict(int)

    def __init__(self, **kwargs):
        self._old_scope = None
        for value in kwargs.values():
            if not isinstance(value, string_types):
                raise ValueError("Attributes need to be string")
        self._attr = kwargs

    def get(self, attr):
        """
        Get the attribute dict given the attribute set by the symbol.

        Parameters
        ----------
        attr : dict of string to string
            The attribute passed in by user during symbol creation.

        Returns
        -------
        attr : dict of string to string
            Updated attributes to add other scope related attributes.
        """
        if self._attr:
            ret = self._attr.copy()
            if attr:
                ret.update(attr)
            return ret
        else:
            return attr if attr else {}

    def __enter__(self):  # pylint: disable=protected-access
        attr = _current.get()._attr.copy()
        attr.update(self._attr)
        self._attr = attr
        # Token can't be pickled and Token.old_value is Token.MISSING if _current.get() uses default value
        self._old_scope = _current.get()
        _current.set(self)
        return self

    def __exit__(self, ptype, value, trace):
        assert self._old_scope
        _current.set(self._old_scope)


_current = contextvars.ContextVar('namemanager', default=AttrScope())


def current():
    """Returns the current name manager."""
    return _current.get()