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nextflow/docs/developer/nextflow.md

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+
+# `nextflow`
+
+The `nextflow` package contains various top-level classes.
+
+## Class Diagram
+
+```{mermaid} diagrams/nextflow.mmd
+```
+
+```{note}
+Some classes may be excluded from the above diagram for brevity.
+```
+
+## Notes
+
+The `Nextflow` class implements several methods that are exposed to Nextflow scripts. See {ref}`stdlib-namespaces-global` for details.
+
+The `Channel` class implements the channel factory methods, and it is exposed directly to Nextflow scripts. See {ref}`channel-factory` for details.
+
+The `Session` class is the top-level representation of a Nextflow run, or "session". See [nextflow.script](nextflow.script.md) for more details about how a `Session` is created.