code: def getISAAssay(assayNum, studyNum, pathToISATABFile):
      
      from isatools import isatab
      import copy
      try:
          isa = isatab.load(pathToISATABFile, skip_load_tables=True)
          std = isa.studies[studyNum - 1]
          return copy.deepcopy(std.assays[assayNum - 1])
      except FileNotFoundError as err:
          raise err
docs: This function returns an Assay object given the assay and study numbers in an ISA file
      Typically, you should use the exploreISA function to check the contents
      of the ISA file and retrieve the assay and study numbers you are interested in!
      :param assayNum: The Assay number (notice it's not zero-based index).
      :type assayNum: int
      :param studyNum: The Study number (notice it's not zero-based index).
      :type studyNum: int
      :param pathToISATABFile: The path to the ISATAB file
      :type pathToISATABFile: str
      :raise FileNotFoundError: If pathToISATABFile does not contain file 'i_Investigation.txt'.