Add molecular data exposure to tardis atom data

tardis/io/atom_data/base.py

@@ -6,6 +6,7 @@
 from astropy import units as u
 from astropy.units import Quantity
 from scipy import interpolate
+from dataclasses import dataclass
 
 from tardis import constants as const
 from tardis.io.atom_data.util import resolve_atom_data_fname
@@ -100,6 +101,11 @@ class AtomData:
         columns: atomic_number, element, Rad energy, Rad intensity decay mode.
         Curated from nndc
 
+    molecule_data : MolecularData
+    A class containing the *molecular data* with:
+        equilibrium_constants, partition_functions, dissociation_energies
+
+
     Attributes
     ----------
     prepared : bool
@@ -116,6 +122,7 @@ class AtomData:
     photoionization_data : pandas.DataFrame
     two_photon_data : pandas.DataFrame
     decay_radiation_data : pandas.DataFrame
+    molecule_data : MolecularData
 
     Methods
     -------
@@ -221,7 +228,14 @@ def from_hdf(cls, fname=None):
             if "linelist" in store:
                 dataframes["linelist"] = store["linelist"]
 
-            atom_data = cls(**dataframes)
+            if "molecules" in store:
+                molecule_data = MoleculeData(
+                    store["molecules/equilibrium_constants"],
+                    store["molecules/partition_functions"],
+                    store["molecules/dissociation_energies"],
+                )
+
+            atom_data = cls(**dataframes, molecule_data=molecule_data)
 
             try:
                 atom_data.uuid1 = store.root._v_attrs["uuid1"]
@@ -284,6 +298,7 @@ def __init__(
         two_photon_data=None,
         linelist=None,
         decay_radiation_data=None,
+        molecule_data=None,
     ):
         self.prepared = False
 
@@ -346,6 +361,9 @@ def __init__(
         if linelist is not None:
             self.linelist = linelist
 
+        if molecule_data is not None:
+            self.molecule_data = molecule_data
+
         if decay_radiation_data is not None:
             self.decay_radiation_data = decay_radiation_data
         self._check_related()
@@ -762,3 +780,29 @@ def get_collision_matrix(self, species, t_electrons):
             )
         )
         return c_ul_matrix + c_lu_matrix.transpose(1, 0, 2)
+
+
+@dataclass
+class MoleculeData(object):
+    """
+    Class to hold molecular data. Held by the AtomData object.
+
+    equilibrium_constants : pandas.DataFrame
+    A DataFrame containing the *molecular equilibrium constants* with:
+        index: molecule
+        columns: temperatures
+
+    partition_functions : pandas.DataFrame
+    A DataFrame containing the *molecular partition functions* with:
+        index: molecule
+        columns: temperatures
+
+    dissociation_energies : pandas.DataFrame
+    A DataFrame containing the *molecular dissociation energies* with:
+        index: molecule
+
+    """
+
+    equilibrium_constants: pd.DataFrame
+    partition_functions: pd.DataFrame
+    dissociation_energies: pd.DataFrame