Insert column into molecule at specified location.

        Wrapper around the :meth:`pandas.DataFrame.insert` method.

def insert(self, loc, column, value, allow_duplicates=False,
               inplace=False):
        """Insert column into molecule at specified location.

        Wrapper around the :meth:`pandas.DataFrame.insert` method.
        """
        out = self if inplace else self.copy()
        out._frame.insert(loc, column, value,
                          allow_duplicates=allow_duplicates)
        if not inplace:
            return out