class_docstr: Class for representing cohort-level genomic data.
  
  This class facilitates a sparse, split representation of genomic data in
  which reference block data and variant data are contained in separate
  :class:`.MatrixTable` objects.
  
  Parameters
  ----------
  reference_data : :class:`.MatrixTable`
      MatrixTable containing only reference block data.
  variant_data : :class:`.MatrixTable`
      MatrixTable containing only variant data.
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code: def _reference_path(base: str) -> str:
      return os.path.join(base, "reference_data")
  
imports: import os
  import hail
  from hail.matrixtable import MatrixTable
  from hail.typecheck import typecheck_method
  from hail.utils.java import info, warning
  from hail.genetics import ReferenceGenome
  import json
label_desc: Use image node_id 1 for calling the VariantDataset obj's underlying member method code with example usage: obj._reference_path(base) and returns: os