old_contents: #!/usr/bin/env python3
  #
  # 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.
  
  import os
  
  import flask
  import requests
  
  from opentelemetry import trace
  from opentelemetry.ext import http_requests
  from opentelemetry.ext.wsgi import OpenTelemetryMiddleware
  from opentelemetry.sdk.trace import TracerProvider
  from opentelemetry.sdk.trace.export import (
      BatchExportSpanProcessor,
      ConsoleSpanExporter,
  )
  
  # The preferred tracer implementation must be set, as the opentelemetry-api
  # defines the interface with a no-op implementation.
  trace.set_tracer_provider(TracerProvider())
  tracer = trace.get_tracer(__name__)
  
  exporter = ConsoleSpanExporter()
  span_processor = BatchExportSpanProcessor(exporter)
  trace.set_tracer_provider(TracerProvider())
  trace.get_tracer_provider().add_span_processor(span_processor)
  
  # Integrations are the glue that binds the OpenTelemetry API and the
  # frameworks and libraries that are used together, automatically creating
  # Spans and propagating context as appropriate.
  http_requests.enable(trace.get_tracer_provider())
  app = flask.Flask(__name__)
  app.wsgi_app = OpenTelemetryMiddleware(app.wsgi_app)
  
  
  @app.route("/")
  def hello():
      with tracer.start_as_current_span("parent"):
          requests.get("https://www.wikipedia.org/wiki/Rabbit")
      return "hello"
  
  
  if __name__ == "__main__":
      app.run(debug=True)
  
new_contents: #!/usr/bin/env python3
  #
  # 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.
  
  import os
  
  import flask
  import requests
  
  from opentelemetry import trace
  from opentelemetry.ext import http_requests
  from opentelemetry.ext.wsgi import OpenTelemetryMiddleware
  from opentelemetry.sdk.trace import TracerProvider
  from opentelemetry.sdk.trace.export import (
      BatchExportSpanProcessor,
      ConsoleSpanExporter,
  )
  
  # The preferred tracer implementation must be set, as the opentelemetry-api
  # defines the interface with a no-op implementation.
  trace.set_tracer_provider(TracerProvider())
  tracer = trace.get_tracer(__name__)
  
  exporter = ConsoleSpanExporter()
  span_processor = BatchExportSpanProcessor(exporter)
  trace.get_tracer_provider().add_span_processor(span_processor)
  
  # Integrations are the glue that binds the OpenTelemetry API and the
  # frameworks and libraries that are used together, automatically creating
  # Spans and propagating context as appropriate.
  http_requests.enable(trace.get_tracer_provider())
  app = flask.Flask(__name__)
  app.wsgi_app = OpenTelemetryMiddleware(app.wsgi_app)
  
  
  @app.route("/")
  def hello():
      with tracer.start_as_current_span("parent"):
          requests.get("https://www.wikipedia.org/wiki/Rabbit")
      return "hello"
  
  
  if __name__ == "__main__":
      app.run(debug=True)
  
subject: Remove duplicated call to set_tracer_provider (#560)