Custom observability spans

[Luke-Shepp]

How can custom spans be started?

The documentation mentions get_tracer() to get the global tracer instance, which contains a few specific start/end span methods such as start_tool_call_span/end_tool_call_span, but _start_span is underscored - is there a reason for this? Is there any other way to add custom spans?

I need to add spans on custom logic around the spans that are automatically generated. Example of existing spans, where I have custom logic between that I need to add tracing support for.