A simple field.

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 0: for ``FILTERS``: list of instances of ``.resources.Field``.

        Returns
        -------
        .resources.Field
            An instance of ``.resources.Field`` with the correct name.

        Example
        -------

        >>> DataQLParser(r'foo', default_rule='FIELD').data
        <Field[foo] />
        >>> DataQLParser(r'foo(1)', default_rule='FIELD').data
        <Field[foo] .foo(1) />
        >>> DataQLParser(r'foo.bar()', default_rule='FIELD').data
        <Field[foo] .foo.bar() />

def visit_field(self, _, children):
        """A simple field.

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 0: for ``FILTERS``: list of instances of ``.resources.Field``.

        Returns
        -------
        .resources.Field
            An instance of ``.resources.Field`` with the correct name.

        Example
        -------

        >>> DataQLParser(r'foo', default_rule='FIELD').data
        <Field[foo] />
        >>> DataQLParser(r'foo(1)', default_rule='FIELD').data
        <Field[foo] .foo(1) />
        >>> DataQLParser(r'foo.bar()', default_rule='FIELD').data
        <Field[foo] .foo.bar() />
        """

        filters = children[0]
        return self.Field(getattr(filters[0], 'name', None), filters=filters)