# Source code for opentelemetry.trace.propagation

    # Copyright The OpenTelemetry Authors
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #     http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.
    from typing import Optional

    from opentelemetry.context import create_key, get_value, set_value
    from opentelemetry.context.context import Context
    from opentelemetry.trace.span import INVALID_SPAN, Span

    SPAN_KEY = "current-span"
    _SPAN_KEY = create_key("current-span")

    def set_span_in_context(
        span: Span, context: Optional[Context] = None
    ) -> Context:
        """Set the span in the given context.

        Args:
            span: The Span to set.
            context: a Context object. if one is not passed, the
                default current context is used instead.
        """
        ctx = set_value(_SPAN_KEY, span, context=context)
        return ctx

    def get_current_span(context: Optional[Context] = None) -> Span:
        """Retrieve the current span.

        Args:
            context: A Context object. If one is not passed, the
                default current context is used instead.

        Returns:
            The Span set in the context if it exists. INVALID_SPAN otherwise.
        """
        span = get_value(_SPAN_KEY, context=context)
        if span is None or not isinstance(span, Span):
            return INVALID_SPAN
        return span