docs: def select_data(db_file, slab=None, facet=None):
      """Gathers relevant data from SQL database generated by CATHUB.
  
      Parameters
      ----------
      db_file : Path to database
      slab : Which metal (slab) to select.
      facet : Which facets to select.
  
      Returns
      -------
      data : SQL cursor output.
      """
      con = sql.connect(db_file)
      cur = con.cursor()
      if slab and facet:
          select_command = 'select chemical_composition, facet, reactants, products, reaction_energy ' \
                       'from reaction where facet='+str(facet)+' and chemical_composition LIKE "%'+slab+'%";'
      elif slab and not facet:
          select_command = 'select chemical_composition, facet, reactants, products, reaction_energy ' \
               'from reaction where chemical_composition LIKE "%'+slab+'%";'
      else:
          select_command = 'select chemical_composition, facet, reactants, products, reaction_energy from reaction;'
      cur.execute(select_command)
      data = cur.fetchall()
      return(data)