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# Source code for astropy.utils.metadata.utils

    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    """This module contains helper functions handling metadata."""

    import numpy as np

    from astropy.utils.misc import dtype_bytes_or_chars

    from .exceptions import MergeConflictError

    __all__ = ["common_dtype"]

    def dtype(arr):
        return getattr(arr, "dtype", np.dtype("O"))

    def common_dtype(arrs):
        """
        Use numpy to find the common dtype for a list of ndarrays.

        Only allow arrays within the following fundamental numpy data types:
        ``np.bool_``, ``np.object_``, ``np.number``, ``np.character``, ``np.void``

        Parameters
        ----------
        arrs : list of ndarray
            Arrays for which to find the common dtype

        Returns
        -------
        dtype_str : str
            String representation of dytpe (dtype ``str`` attribute)
        """
        np_types = (np.bool_, np.object_, np.number, np.character, np.void)
        uniq_types = {
            tuple(issubclass(dtype(arr).type, np_type) for np_type in np_types)
            for arr in arrs
        }
        if len(uniq_types) > 1:
            # Embed into the exception the actual list of incompatible types.
            incompat_types = [dtype(arr).name for arr in arrs]
            tme = MergeConflictError(f"Arrays have incompatible types {incompat_types}")
            tme._incompat_types = incompat_types
            raise tme

        arrs = [np.empty(1, dtype=dtype(arr)) for arr in arrs]

        # For string-type arrays need to explicitly fill in non-zero
        # values or the final arr_common = .. step is unpredictable.
        for i, arr in enumerate(arrs):
            if arr.dtype.kind in ("S", "U"):
                arrs[i] = [
                    ("0" if arr.dtype.kind == "U" else b"0")
                    * dtype_bytes_or_chars(arr.dtype)
                ]

        arr_common = np.array([arr[0] for arr in arrs])
        return (
            arr_common.dtype.str
            if arr_common.dtype.names is None
            else arr_common.dtype.descr
        )