diff --git a/astro_plasma/core/datasift.py b/astro_plasma/core/datasift.py
index 35d2ac4..920df5a 100644
--- a/astro_plasma/core/datasift.py
+++ b/astro_plasma/core/datasift.py
@@ -9,16 +9,22 @@
 import numpy as np
 from itertools import product
 from pathlib import Path
-from typing import Callable, Optional, Union, Tuple, List, Set
+from typing import Protocol, Callable, Optional, Union, Tuple, List, Set
 import h5py
 import sys
 
 _warn = False
 
 
+class inherited_from_DataSift(Protocol):
+    # This must be compulsorily implemented by any class inheriting from DataSift
+    _check_and_download: Callable
+
+
 class DataSift(ABC):
     def __init__(
         self: "DataSift",
+        child_obj: "inherited_from_DataSift",
         data: h5py.File,
     ) -> None:
         """
@@ -36,7 +42,7 @@ def __init__(
 
         self.batch_size = np.prod(np.array(data["header/batch_dim"]))
         self.total_size = np.prod(np.array(data["header/total_size"]))
-        self._check_and_download: Optional[Callable] = None  # mandatory to be implemented by inheriting classes
+        self._check_and_download = child_obj._check_and_download
 
     def _identify_batch(self: "DataSift", i: int, j: int, k: int, m: int) -> int:
         batch_id = self._get_counter(i, j, k, m) // self.batch_size
@@ -450,9 +456,8 @@ def _interpolate(
                     _argument.append(argument_collection[arg_pos][0])
                 else:
                     _argument.append(argument_collection[arg_pos][indx])
-                if not (_dummy) and _array_argument[arg_pos]:
-                    _reference = np.zeros_like(argument_collection[arg_pos]).reshape(_input_shape)
-            i_vals, j_vals, k_vals, m_vals = self._identify_pos_in_each_dim(*_argument)
+            nH_this, temperature_this, metallicity_this, redshift_this = _argument
+            i_vals, j_vals, k_vals, m_vals = self._identify_pos_in_each_dim(nH_this, temperature_this, metallicity_this, redshift_this)
 
             """
             The trick is to take the floor value for interpolation only if it is the
diff --git a/astro_plasma/core/ionization.py b/astro_plasma/core/ionization.py
index c25368f..8414bd8 100644
--- a/astro_plasma/core/ionization.py
+++ b/astro_plasma/core/ionization.py
@@ -39,10 +39,10 @@ def __init__(
         None.
 
         """
+        self._check_and_download = download_ionization_data
         self.base_url_template = BASE_URL_TEMPLATE
         self.file_name_template = FILE_NAME_TEMPLATE
         self.base_dir = base_dir
-        self._check_and_download = download_ionization_data
 
     @property
     def base_dir(self):
@@ -57,23 +57,9 @@ def base_dir(
 
         fetch(urls=DOWNLOAD_IN_INIT, base_dir=self._base_dir)
         data = h5py.File(self._base_dir / DOWNLOAD_IN_INIT[0][1], "r")
-        super().__init__(data)
+        super().__init__(self, data)
         data.close()
 
-    """
-    def _fetch_data(self: "Ionization", batch_ids: Set[int]) -> None:
-        urls = []
-        for batch_id in batch_ids:
-            urls.append(
-                (
-                    self.base_url_template.format(batch_id),
-                    Path(self.file_name_template.format(batch_id)),
-                )
-            )
-
-        fetch(urls=urls, base_dir=self.base_dir)
-    """
-
     def _get_file_path(self: "Ionization", batch_id: int) -> Path:
         return self.base_dir / self.file_name_template.format(batch_id)
 
diff --git a/astro_plasma/core/spectrum.py b/astro_plasma/core/spectrum.py
index 941a269..1956e5d 100644
--- a/astro_plasma/core/spectrum.py
+++ b/astro_plasma/core/spectrum.py
@@ -41,10 +41,10 @@ def __init__(
         None.
 
         """
+        self._check_and_download = download_emission_data
         self.base_url_template = BASE_URL_TEMPLATE
         self.file_name_template = FILE_NAME_TEMPLATE
         self.base_dir = base_dir
-        self._check_and_download = download_emission_data
 
     @property
     def base_dir(self):
@@ -59,24 +59,10 @@ def base_dir(
 
         fetch(urls=DOWNLOAD_IN_INIT, base_dir=self._base_dir)
         data = h5py.File(self._base_dir / DOWNLOAD_IN_INIT[0][1], "r")
-        super().__init__(data)
+        super().__init__(self, data)
         self._energy = np.array(data["output/energy"])
         data.close()
 
-    """
-    def _fetch_data(self: "EmissionSpectrum", batch_ids: Set[int]) -> None:
-        urls = []
-        for batch_id in batch_ids:
-            urls.append(
-                (
-                    self.base_url_template.format(batch_id),
-                    Path(self.file_name_template.format(batch_id)),
-                )
-            )
-
-        fetch(urls=urls, base_dir=self.base_dir)
-    """
-
     def _get_file_path(self: "EmissionSpectrum", batch_id: int) -> Path:
         return self.base_dir / self.file_name_template.format(batch_id)