Class used for declaring PipelineTask prerequisite connections
Parameters
----------
name : `str`
The default name used to identify the dataset type
storageClass : `str`
The storage class used when (un)/persisting the dataset type
multiple : `bool`
Indicates if this connection should expect to contain multiple objects
of the given dataset type
dimensions : iterable of `str`
The `lsst.daf.butler.Butler` `lsst.daf.butler.Registry` dimensions used
to identify the dataset type identified by the specified name
deferLoad : `bool`
Indicates that this dataset type will be loaded as a
`lsst.daf.butler.DeferredDatasetHandle`. PipelineTasks can use this
object to load the object at a later time.
lookupFunction: `typing.Callable`, optional
An optional callable function that will look up PrerequisiteInputs
using the DatasetType, registry, quantum dataId, and input collections
passed to it. If no function is specified, the default temporal spatial
lookup will be used.
Notes
-----
Prerequisite inputs are used for datasets that must exist in the data
repository before a pipeline including this is run; they cannot be produced
by another task in the same pipeline.
In exchange for this limitation, they have a number of advantages relative
to regular `Input` connections:
- The query used to find them then during `QuantumGraph` generation can be
fully customized by providing a ``lookupFunction``.
- Failed searches for prerequisites during `QuantumGraph` generation will
usually generate more helpful diagnostics than those for regular `Input`
connections.
- The default query for prerequisite inputs relates the quantum dimensions
directly to the dimensions of its dataset type, without being constrained
by any of the other dimensions in the pipeline. This allows them to be
used for temporal calibration lookups (which regular `Input` connections
cannot do at present) and to work around `QuantumGraph` generation
limitations involving cases where naive spatial overlap relationships
between dimensions are not desired (e.g. a task that wants all detectors
in each visit for which the visit overlaps a tract, not just those where
that detector+visit combination overlaps the tract).
Definition at line 204 of file connectionTypes.py.