add samples for exemplar filter and custom reservoir factory

docs/examples/metrics/reader/preferred_exemplarfilter.py

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+# 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 time
+
+from opentelemetry.metrics import get_meter_provider, set_meter_provider
+from opentelemetry.sdk.metrics import Counter, MeterProvider
+from opentelemetry.sdk.metrics.export import (
+    ConsoleMetricExporter,
+    PeriodicExportingMetricReader,
+)
+from opentelemetry.sdk.metrics._internal.exemplar import (
+    AlwaysOffExemplarFilter,
+    AlwaysOnExemplarFilter,
+    TraceBasedExemplarFilter,
+)
+
+# Create an ExemplarFilter instance (e.g., TraceBasedExemplarFilter)
+exemplar_filter = TraceBasedExemplarFilter()
+
+exporter = ConsoleMetricExporter()
+
+reader = PeriodicExportingMetricReader(
+    exporter,
+    export_interval_millis=5_000,
+)
+
+# Set up the MeterProvider with the ExemplarFilter
+provider = MeterProvider(
+    metric_readers=[reader],
+    exemplar_filter=exemplar_filter,  # Pass the ExemplarFilter to the MeterProvider
+)
+set_meter_provider(provider)
+
+meter = get_meter_provider().get_meter("exemplar-filter-example", "0.1.2")
+counter = meter.create_counter("my-counter")
+
+for value in range(10):
+    counter.add(value)
+    time.sleep(2.0)

docs/examples/metrics/views/change_reservoir_factory.py

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+# 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 random
+import time
+
+from opentelemetry.metrics import get_meter_provider, set_meter_provider
+from opentelemetry.sdk.metrics import Counter, MeterProvider
+from opentelemetry.sdk.metrics.export import (
+    ConsoleMetricExporter,
+    PeriodicExportingMetricReader,
+)
+from opentelemetry.sdk.metrics.view import View
+from typing import Callable, Optional, Set, Type, Any, Sequence
+from opentelemetry.sdk.metrics._internal.aggregation import (
+    Aggregation,
+    DefaultAggregation,
+    _Aggregation,
+    _ExplicitBucketHistogramAggregation,
+    _ExponentialBucketHistogramAggregation,
+)
+from opentelemetry.sdk.metrics._internal.exemplar import (
+    AlignedHistogramBucketExemplarReservoir,
+    ExemplarReservoir,
+    ExemplarReservoirFactory,
+    SimpleFixedSizeExemplarReservoir
+)
+
+# Returns a factory for creating an exemplar reservoir based on the aggregation type and specified parameters
+def generalized_reservoir_factory(size: int = 1, boundaries: Sequence[float] = None) -> Callable[[Type[_Aggregation]], ExemplarReservoirFactory]:
+        def factory(aggregationType: Type[_Aggregation]) -> ExemplarReservoirFactory:
+            if issubclass(aggregationType, _ExplicitBucketHistogramAggregation):
+                return lambda **kwargs: AlignedHistogramBucketExemplarReservoir(boundaries=boundaries or [], **{k: v for k, v in kwargs.items() if k != 'boundaries'})
+            else:
+                return lambda **kwargs: SimpleFixedSizeExemplarReservoir(size=size, **kwargs)
+
+        return factory
+
+# Create a custom reservoir factory with specified parameters
+custom_reservoir_factory = generalized_reservoir_factory(size=10)
+
+# Create a view with the custom reservoir factory
+change_reservoir_factory_view= View(
+                instrument_name="my.counter",
+                name="name",
+                aggregation=DefaultAggregation(),
+                exemplar_reservoir_factory=custom_reservoir_factory,
+            )
+
+# Use console exporter for the example
+exporter = ConsoleMetricExporter()
+
+# Create a metric reader with stdout exporter
+reader = PeriodicExportingMetricReader(exporter, export_interval_millis=1_000)
+provider = MeterProvider(
+    metric_readers=[
+        reader,
+    ],
+    views=[
+        change_reservoir_factory_view,
+    ],
+)
+set_meter_provider(provider)
+
+meter = get_meter_provider().get_meter("reservoir-factory-change", "0.1.2")
+
+my_counter = meter.create_counter("my.counter")
+
+while 1:
+    my_counter.add(random.randint(1, 10))
+    time.sleep(random.random())