code: def read(filename, file_format=None):
      
      # https://stackoverflow.com/q/4843173/353337
      assert isinstance(filename, str)
  
      if not file_format:
          # deduce file format from extension
          file_format = _filetype_from_filename(filename)
  
      format_to_reader = {
          "ansys": ansys_io,
          "ansys-ascii": ansys_io,
          "ansys-binary": ansys_io,
          #
          "gmsh": msh_io,
          "gmsh-ascii": msh_io,
          "gmsh-binary": msh_io,
          "gmsh2": msh_io,
          "gmsh2-ascii": msh_io,
          "gmsh2-binary": msh_io,
          "gmsh4": msh_io,
          "gmsh4-ascii": msh_io,
          "gmsh4-binary": msh_io,
          #
          "med": med_io,
          "medit": medit_io,
          "dolfin-xml": dolfin_io,
          "permas": permas_io,
          "moab": h5m_io,
          "off": off_io,
          #
          "stl": stl_io,
          "stl-ascii": stl_io,
          "stl-binary": stl_io,
          #
          "vtu-ascii": vtu_io,
          "vtu-binary": vtu_io,
          #
          "vtk-ascii": vtk_io,
          "vtk-binary": vtk_io,
          #
          "xdmf": xdmf_io,
          "exodus": exodus_io,
          #
          "abaqus": abaqus_io,
          #
          "mdpa": mdpa_io,
      }
  
      assert file_format in format_to_reader, "Unknown file format '{}' of '{}'.".format(
          file_format, filename
      )
  
      return format_to_reader[file_format].read(filename)
docs: Reads an unstructured mesh with added data.
  
      :param filenames: The files to read from.
      :type filenames: str
  
      :returns mesh{2,3}d: The mesh data.